Conditions: Hypercapnia Ventilatory Depression
Allocation: RANDOMIZED | Intervention model: CROSSOVER
Enrollment: 27
Healthy volunteers: yes

Brief summary:
This study is designed to evaluate the effects of the coadministration of paroxetine or escitalopram with an opioid on ventilation. Ventilation will be assessed using a rebreathing methodology. This study will evaluate chronic and acute dosing of paroxetine and escitalopram combined with an opioid as well as chronic and acute dosing of the two drugs without coadministration of an opioid.

This study is a 3-period, randomized, placebo-controlled crossover study conducted with 25 healthy participants. Each participant will receive each of the 3 treatments (placebo/oxycodone, paroxetine/oxycodone, escitalopram/oxycodone) in a randomized order.

Detailed description:
This study is designed to evaluate the effects of the coadministration of paroxetine or escitalopram, two selective serotonin reuptake inhibitors (SSRI), with an opioid on hypercapnic ventilation. Hypercapnic ventilation will be assessed under both hyperoxic and hypoxic conditions using the Duffin rebreathing method. This method allows for critical physiological measurements and thresholds to be captured that can then be used to model the effects of drugs when there are dynamic changes in oxygen partial pressure (PO2) and carbon dioxide partial pressure (PCO2), such as during a real-world opioid overdose.

SSRIs take approximately 3 weeks to reach maximal therapeutic effect, which correlates with the time required for pre-synaptic inhibitory serotonergic receptors to desensitize. Therefore, drug-effects on ventilation should be evaluated under steady state conditions.

This study is randomized, placebo-controlled crossover study which includes three 21-day periods conducted with 25 healthy participants. Participants will receive each of the 3 treatments (placebo/oxycodone, paroxetine/oxycodone, or escitalopram/oxycodone) in a randomized order. Paroxetine dosing will range from 40-60 mg once daily (QD) and escitalopram dosing will range from 20-30 mg QD. Subjects will receive 10 mg oxycodone on three different days each period. Subjects will undergo 6 days of rebreathing and time-matched pupillary assessments along with 3 separate days of ECG assessments each period. Additionally, blood samples will be collected for determination of plasma concentrations for each study drug on days with rebreathing and ECG assessments.

Arms:
arm 1: Participants will receive placebo on days 1-21 for this treatment period. Oxycodone will be administered on days 6, 12, and 21 of this treatment period. arm 2: Participants will receive paroxetine on days 1-21 for this treatment period. Oxycodone will be administered on days 6, 12, and 21 of this treatment period. arm 3: Participants will receive escitalopram on days 1-21 for this treatment period. Oxycodone will be administered on days 6, 12, and 21 of this treatment period.

Interventions: intervention 1: Placebo and Oxycodone intervention 2: Paroxetine and Oxycodone intervention 3: Escitalopram and Oxycodone
Intervention descriptions: intervention 1: Participants will receive placebo on days 1-21 for this treatment period. Oxycodone 10 mg (2 x 5 mg tablets) will be administered on days 6, 12, and 21 of this treatment period. intervention 2: Participants will receive 40 mg paroxetine (2 x 20 mg tablets) on days 1-6 and 60 mg paroxetine (3 x 20 mg tablets) on days 7-21 for this treatment period. Oxycodone 10 mg (2 x 5 mg tablets) will be administered on days 6, 12, and 21 of this treatment period. intervention 3: Participants will receive 20 mg escitalopram (2 x 10 mg tablets) on days 1-6 and 30 mg escitalopram (3 x 10 mg tablets) on days 7-21 for this treatment period. Oxycodone 10 mg (2 x 5 mg tablets) will be administered on days 6, 12, and 21 of this treatment period.

Protocol document:
ICF_002.pdf: 
Study Title: Clinical Study to investigate the effect of administration of selective 
serotonin reuptake inhibitors and an opioid on ventilation 
 
Document Title: Informed Consent Form – Study No. SCR-012 
 
Document Date: 30 March 2023 
 
NCT Number: NCT05470465 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 1 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
CONSENT TO TAKE PART IN A CLINICAL RESEARCH STUDY 
AND 
AUTHORIZATION TO DISCLOSE HEALTH INFORMATION 
 
Sponsor/Study Title: 
  
U.S. Food and Drug Administration, “Clinical Study to Investigate the 
Effect of Administration of Selective Serotonin Reuptake Inhibitors and 
an Opioid on Ventilation” 
 
Protocol Number: 
 
SCR-012 
Principal Investigator: 
(Study Doctor)  
 
Jan Matousek, D.O. 
Telephone: 
 
800.597.4507 (Recruitment Department) 
855.622.8100 (24-hour urgent question/care) 
 
Additional Contact(s): 
Trupti I., Project Manager 
Karrielynn G., Study Manager 
Samuel B., Associate Study Manager 
 
 
Address: 
 
 
Spaulding Clinical Research, LLC 
525 S Silverbrook Dr. 
West Bend, WI 53095 
 
SUBJECT SCREENING #_______ 
 
Please read this form carefully. Take time to ask the study doctor or study staff as many questions about 
the study as you would like. The study doctor or study staff can explain words or information that you do 
not understand. Reading this form and talking to the study doctor or study staff may help you decide 
whether to take part or not. If you decide to take part in this study, you must sign your name at the end of 
this form. You cannot take part in this research study until you sign and date this form. 
 
WHAT IS A VOLUNTEER INFORMED CONSENT? 
 
You are being asked to take part in a research study which will look at three things:  
• 
Assess whether dosing of two different selective serotonin reuptake inhibitors (SSRIs) viz. 
paroxetine and escitalopram combined with oxycodone (narcotic analgesic) affect breathing 
compared to oxycodone alone under different gas levels (hyperoxic [more oxygen] and hypoxic 
[less oxygen] conditions), 
• 
Assess whether dosing of SSRIs combined with oxycodone has effects on breathing compared to 
oxycodone alone under different gas levels, and 
• 
Assess whether dosing of SSRIs has effects on breathing compared to placebo under different gas 
levels.   
 
Oxycodone HCl (referred to throughout this document as oxycodone), Paroxetine HCl (referred to 
throughout this document as paroxetine), and Escitalopram oxalate (referred to throughout this document 
as escitalopram) have been approved by the U.S. Food and Drug Administration. Oxycodone is used for 
the management of pain severe enough to require an opioid. Paroxetine is used for the treatment of major 
depressive disorder. Escitalopram is used for acute and maintenance treatment of major depressive 
disorder and acute treatment of generalized anxiety disorder. However, their use in this study is 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 2 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
investigational. An investigational use is one that is not approved by the U.S. Food and Drug 
Administration. 
 
Before you decide to take part, you should understand the possible benefits and risks associated with this 
study. This process is known as informed consent and means that you will: 
 
• 
Receive detailed information about this research study. 
• 
Have a chance to ask and receive answers to any questions you may have. 
• 
Be asked to read and sign this informed consent, once you understand the study and wish to take 
part. 
• 
Be given a signed and dated copy of this informed consent to keep. 
 
Taking part in this study is entirely voluntary. 
 
WHY ARE THESE DRUGS BEING STUDIED? 
 
A well-known and potentially fatal adverse reaction (side effect) associated with opioid administration, 
particularly in the scenario of misuse, abuse, or when co-administered with certain other drugs is that 
people ‘stop breathing’. Research suggests this is caused by a reduced breathing response to counteract 
increasing levels of carbon dioxide (CO2). In August 2016, the U.S. Food and Drug Administration 
included boxed warnings about increased potential for decreased breathing with co-use of 
benzodiazepines and opioids. In response to this action, concerns were raised because patients may be 
prescribed other psychotropic drugs (drugs that affect a person’s mental state) that may have similar 
negative reactions when combined with opioids. 
 
Non-clinical and clinical studies have shown different SSRIs can have independent effects on breathing, 
though SSRIs have not been shown to cause severe decreased breathing on their own. This supports the 
need for additional investigation on the effects of serotonergic drugs (paroxetine and escitalopram). 
 
Special Procedure: Duffin Rebreathing Procedure 
 
You will be participating in the Duffin rebreathing procedure where you will breathe a hyperoxic (more 
oxygen)-hypercapnic (more carbon dioxide) (24% O2, 6% CO2, N2 balanced) or hypoxic (less oxygen)-
hypercapnic (more carbon dioxide) (6% O2, 6% CO2, N2 balanced) gas mixture through a tight-fitting 
mask. This mixture of oxygen, carbon dioxide and nitrogen provided will be different than is normally 
found in room air (21% O2, 0.04% CO2, N2 balanced with minor amounts of other gasses). The different 
gas mixtures, in particular the higher level of carbon dioxide breathed in, may result in a feeling of 
needing to breathe faster or more deeply. This procedure has been used in many previous studies and is 
non-invasive, meaning no pieces of equipment enter your body. During screening, you will be shown the 
rebreathing equipment and will be trained how to use it to understand if the procedure is tolerable. By 
performing this and receiving the drugs in the study as outlined in this informed consent form (ICF), the 
data collected will help the U.S. Food and Drug Administration to better understand how these drugs can 
be given more safely. 
 
You will have Duffin Rebreathing explained to you at length during the ICF process, and you will have 
time to ask as many questions about this as you wish. The procedure will be conducted under medical 
supervision.  
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 3 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
 
Figure 1: Rebreathing Procedure Equipment Setup 
 
 
WHO IS BEING ASKED TO TAKE PART IN THIS STUDY? 
 
Approximately 25 healthy male and female adult subjects, who meet the requirements following a 
screening visit, will be enrolled in the study.   
 
You have been asked to take part in this study because you are in general good health, are 18-50 
(inclusive) years of age, have no history of heart or liver disease, no history of allergies, and have not 
participated in another research study for an experimental drug (or a medical device) within 30 days of 
the first dose of study drug. 
 
HOW MUCH TIME IS REQUIRED TO TAKE PART IN THE STUDY? 
 
If you decide to take part in the study, you will be asked to attend a screening visit. If you pass the 
screening visit, you will return to the clinic for 3 inpatient periods. Each period will last for 23 days/22 
nights. There will be 21 days between each inpatient period. By the end of this study you will have spent 
at least 69 days and 66 nights in the clinic, with at least 21 days off in between each period. 
 
The duration of your participation in the study from screening to final follow-up will be up to 134 days. 
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 4 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
INFORMATION FOR FEMALE SUBJECTS 
 
You should not screen for this study if: 
 
• 
There is any possibility that you may become, or are pregnant, 
• 
You have given birth in the last 3 months, or 
• 
You are breast feeding. 
 
You may screen for this study if: 
 
• 
You are of non-childbearing potential (confirmed with a blood draw to measure follicle-
stimulating hormone levels greater than 40 mIU/mL) 
• 
You have been strictly abstinent for 1 month before check-in (Day -1) and agree to remain strictly 
abstinent for the duration of the study and for at least 1 month after the last application of study 
drug.  
• 
You are using two adequate methods of contraception to avoid pregnancy throughout the study 
and for at least 1 month after last study drug administration.  
 
Adequate methods of contraception include use of two of the following categories of which one (1) must 
be a barrier method from at least 1 month before check-in (Day -1) until at least 1 month after the end of 
the study. 
 
• 
Hormonal implants/patch,  
• 
Oral hormonal contraceptives,  
• 
Injectable hormones,  
• 
Intra-uterine device (IUD), 
• 
Approved cervical ring,  
• 
Diaphragm with spermicide or condom (female or male) with spermicide 
 
The use of spermicide alone and condom alone are not acceptable methods of contraception.   
 
Except for continuous abstinence (no sexual intercourse with a male partner), no method of birth control 
can be considered 100% reliable in preventing pregnancy. Although the risk of becoming pregnant is low 
with many methods, unplanned pregnancies may occur with all birth control methods. Most occur 
because of improper or irregular use of the birth control method.  If you are usually not sexually active 
but become sexually active, you must follow the advice documented above regarding contraceptive 
methods. 
 
All females enrolled in this study will have a pregnancy test performed at screening, before admission 
periods (Day -1, Day 42, and Day 84) and/or early exit visits. 
 
Please be aware that a pregnancy test may not be positive until 12 days after conception (fertilization of 
the egg by sperm). Therefore, if you do not follow the study birth control requirements and/or your birth 
control method has failed, you will not be able to count on a negative test to confirm that you are not 
pregnant. 
 
If you know that you have not followed the study birth control requirements outlined above, then you 
must immediately inform us. You must not take any dose of the study drug if you have not followed these 
requirements.  
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 5 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
INFORMATION FOR MALE SUBJECTS   
 
You must agree to practice 2 highly effective methods of birth control (as listed above) from at least 1 
month before check-in (Day -1) until at least 2 months after the last dose of study drug. The effect of the 
study drug on male sperm is unknown. In rare cases, drugs may damage sperm in ways that affect a child 
that is fathered. Affected sperm may be present in the semen for about 2 months. Therefore, it is 
recommended to avoid fathering a child for 2 months after the last dose of the study drug. 
 
Periodic abstinence and withdrawal are not acceptable methods of contraception. 
 
HOW WILL YOU KNOW IF YOU ARE ELIGIBLE TO TAKE PART? 
 
You will need to fast for at least 8 hours prior to your arrival at Spaulding Clinical Research, LLC. for 
your screening visit, meaning you should not eat any food and should only have water to drink. 
 
At the beginning of the Screening visit, Informed Consent will be obtained. 
 
Before starting the study, the following screening procedures will be performed: 
 
• 
A complete medical history and physical examination (including height and weight 
measurements for Body Mass Index [BMI, a way to tell if your weight is proportional to your 
height]). 
• 
Assessment of blood pressure, respiratory rate, heart rate, and oral temperature and pulse 
oximetry. 
• 
A complete history of relevant allergies or drug sensitivities. 
• 
An electrocardiogram (ECG), (a painless recording of the electrical activity of your heart). 
• 
You will be asked if you have taken any medication recently. 
• 
You will be asked if you have been feeling ill recently. 
• 
Clinical laboratory tests (urine and blood samples), including screening for drugs, alcohol, and 
pregnancy tests (all female subjects), and testing for HIV, hepatitis B and C. Positive results of 
HIV or hepatitis tests will be reported to local health authorities as required by state law. 
• 
Perform Duffin’s Rebreathing under hyperoxic and hypoxic conditions 
 
If you meet the “entry criteria” of the study, according to the study doctor, you will be tested again when 
you are admitted to Spaulding Clinical Research, LLC. You will have the entry criteria reviewed again to 
ensure that you still are eligible for the study.  
In addition, prior to admission you will have a diagnostic test performed to detect severe acute respiratory 
syndrome coronavirus 2 (called “coronavirus” from now on), which is the virus that causes COVID-19. 
Depending on the time required to return results, this may be performed ~2 days before check-in or may 
be performed on the check-in day. You will only be allowed to be admitted if your coronavirus test is 
negative. In addition, when entering the building for screening and check-in, triage for COVID-19 will 
take place. The exact details of what will occur at triage may change as additional information or testing 
is available, however as of now it is planned to include asking about any potential contacts with COVID-
19, signs and symptoms associated with COVID-19, temperature monitoring and antibody screening for 
coronavirus. 
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 6 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
HOW WILL THE STUDY BE DONE? 
 
Approximately 25 healthy adult subjects, both male and female will be enrolled in this study. The study 
will consist of 3 treatment periods of 23 days/ 22 nights each with a 21-day wash-out in between each 
period. All subjects will be randomized (placed by chance) into a treatment group. Subjects will receive 
the following 3 treatments in a randomized order over the 3 treatment periods: 
 
Study 
Treatment 
Day 
1-5 
6 
7-11 
12 
13-20 
21 
A 
Placebo QD 
Placebo +  
10 mg  
oxycodone 
Placebo QD 
Placebo + 
10 mg  
oxycodone 
Placebo QD 
Placebo +  
10 mg 
oxycodone 
B 
40 mg 
paroxetine QD 
40 mg 
paroxetine + 10 
mg  
oxycodone 
60 mg 
paroxetine QD 
60 mg 
paroxetine + 
10 mg  
oxycodone 
60 mg 
paroxetine QD 
60 mg 
paroxetine + 
10 mg  
oxycodone 
C 
20 mg 
escitalopram 
QD 
20 mg 
escitalopram + 
10 mg 
oxycodone 
30 mg 
escitalopram 
QD 
30 mg 
escitalopram + 
10 mg  
oxycodone 
30 mg 
escitalopram 
QD 
30 mg 
escitalopram + 
10 mg 
oxycodone 
 
 
Once the study doctor determines that you are eligible to participate, you will be enrolled into one of the 
groups above for the first period. You will not be allowed to choose your group or the order in which you 
receive the study treatments. Because this is a double blinded study, neither you nor the study doctor or 
study staff will know which study treatment you are receiving. 
 
A placebo is a medically inactive substance which looks like the study drug. 
 
QD means to take the medication once daily. 
 
Ondansetron will also be administered prior to all oxycodone doses to reduce potential nausea/vomiting 
side effects. 
 
You will have received all 3 of the above study treatments by the end of the study. There will be 
about 21 days in between each study treatment period. 
 
You will go through the same tests and procedures described below for any of the study treatments you 
receive.  
 
WHAT TESTS AND PROCEDURES WILL BE USED IN THE STUDY? 
 
Check In (Days -1, 42, and 84) 
 
Upon admission to Spaulding Clinical Research, LLC., you will be given an identity band to wear 
throughout your entire stay in the unit. 
 
You will need to fast for at least 8 hours prior to your arrival at Spaulding Clinical Research, LLC. for 
your check-in, meaning you should not eat any food and should only have water to drink.  
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 7 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
The following admission procedures will be performed:  
 
• 
Perform/review results from coronavirus test.  
• 
Medical history updates. 
• 
Physical examination.  
• 
Clinical laboratory tests (urine and blood samples), including screening for drugs, alcohol, 
and pregnancy tests (all female subjects).  
• 
Assessment of blood pressure, respiratory rate, heart rate, and oral temperature. 
• 
An electrocardiogram (ECG), (a painless recording of the electrical activity of your heart). 
• 
A pulse oximetry recording (painless recording of the oxygen levels in your blood). 
• 
You will be asked for details of any medication taken since the screening or previous visit. 
• 
You will be asked if you have been ill since the screening or previous visit. 
• 
You will be asked if you complied with study restrictions. 
• 
Perform Duffin’s Rebreathing under hyperoxic and hypoxic conditions.  
• 
You will be provided meals (lunch, dinner and a snack). 
• 
Inclusion/Exclusion assessment and preparation for randomization (Day -1). Randomization 
means that you will be assigned by chance, like the flip of a coin, to either study group. 
 
The results from these tests will help the study staff determine whether you are still eligible to enter the 
study.  
 
Study Treatment (Days 1 to 21, 43 to 63, and 85 to 105) 
 
• 
Adverse event assessment and changes in concomitant medications. 
• 
Pharmacokinetic (PK) blood sampling. 
• 
Meals (after last Duffin Rebreathing procedure – lunch, dinner and a snack). 
• 
Clinical laboratory tests (urine and blood samples) 
• 
Assessment of blood pressure, heart rate, respiratory rate and oral temperature.  
• 
Administration of study product. 
• 
Continuous ECG (continuous, painless recordings of your heart’s rhythm)  
• 
Continuous pulse oximetry monitoring. 
• 
Duffin Rebreathing procedure by trained study staff.  
• 
Eye assessments to measure pupil size. 
• 
Sedation assessments to measure whether you feel awake/alert vs. sedated. 
 
Washout (Days 23 to 41 and 65 to 83) 
 
• 
Adverse event assessment.  
• 
Physical examination.  
• 
Assessment of blood pressure, heart rate, respiratory rate and oral temperature. 
• 
A pulse oximetry recording (painless recording of the oxygen levels in your blood). 
 
Check Out (Day 22 and 64)  
 
• 
Adverse event assessment and changes in concomitant medications. 
• 
Physical examination.  
• 
Pharmacokinetic (PK) blood sampling. 
• 
Assessment of blood pressure, heart rate, respiratory rate, pulse oximetry and oral 
temperature.  


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 8 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
 
Discharge (Day 106) 
 
• 
Adverse event assessment and changes in concomitant medications. 
• 
Clinical laboratory tests (urine and blood samples) including pregnancy testing for all female 
subjects.  
• 
Physical examination.  
• 
Pharmacokinetic (PK) blood sampling. 
• 
Assessment of blood pressure, heart rate, respiratory rate and oral temperature.  
• 
An electrocardiogram (ECG), (a painless recording of the electrical activity of your heart). 
• 
Discharge from Spaulding Clinical after all events are completed. 
 
 
WHAT TESTS AND PROCEDURES WILL BE USED IN THE STUDY? 
 
Blood Sampling 
 
Blood samples will be collected for measurement of levels of oxycodone and oxymorphone (Days 6, 12 
and 21 of each study period) as well as paroxetine and escitalopram (Days 2, 5, 6, 11, 12, 16, 20, and 21 
of each study period) at approximately the following times: 
 
• 
Day 5, 6, 11, 12, 20, 21 at pre-dose (0 hour), 3, 4, 5, and 8 for a total of approximately 30 blood 
collections for determining study drug levels.  
• 
Day 6, 12, and 21 at 24 hrs for a total of approximately 3 blood collections for determining study 
drug levels. 
• 
Day 2 and 16 at 0 (pre-dose), 2, 3, 4, 5, 6, 8, 12, and 24 hrs post-dose for a total of 
approximately 18 blood collections for determining study drug levels. 
• 
The total number of blood draws is approximately 153 blood collections.  
 
You will have numerous blood samples drawn during the entire study for study drug levels as shown 
above, and 8 safety laboratory draws throughout the study. The blood samples may be taken by individual 
needle sticks into one of your arm veins, or, if necessary, by an indwelling catheter (a thin plastic tube 
placed in a vein in your arm).  
 
The total amount of blood taken for the entire study will be approximately 808 mL or about 3.5 cups for 
the entire study. 
 
Urine Sampling 
 
You will have urine samples collected at screening, each check-in day (Day -1,  Day 42, Day 84) and Day 
106 (Check Out). These will be used to screen for either alcohol or drugs, and for routine safety analysis. 
 
ECG Measurements 
 
Safety ECG measurements will occur at your screening visit, Day -1 (Check In), and Day 106 (Check 
Out). On Days 1, 2 and 16 of each study period you will have telemetry (continuous, painless recordings 
of your heart’s rhythm). There will be periods of time where you will need to lie very still to get precise 
readings of your heart’s rhythm. You will have an ECG assessment on Day 1 of each study period at 0 
(pre-dose) hr. You will have continuous ECG monitoring on Days 2 and Day 16 of each study period and 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 9 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
will require you to lay still for approximately 20 minutes at the following time points (based on the time 
of the study drug dose): 0 hr (Predose), 2 hr, 3 hr, 4 hr, 5 hr, 6 hr, 8 hr, 12 hr, and 24 hr.  
 
Some individuals may develop redness, irritation, or discoloration of the skin at the site of ECG 
electrodes placed on the chest/body. This may develop due to sensitivity to the electrodes or to our skin 
preparation procedure. In order to get the quality results we need, it is necessary for us lightly scrub the 
skin with an abrasive pad to remove any skin impedance such as oil, dead skin cells and lotions. We may 
trace each electrode site with a permanent marker to assure electrodes are placed in the same place on the 
body for each ECG event to maintain quality and consistent results. This tracing may occur as often as 
once a day during study confinement. 
 
Pulse Oximetry 
 
You will have continuous pulse oximetry monitoring (continuous, painless monitoring of oxygen levels in 
your blood) on each of the rebreathing days (Days 5, 6, 11, 12, 20, and 21 of each study period) for 24 
hours. You will also have pulse oximetry measurements with each vital signs collection. 
 
Sedation Assessments 
 
You will have sedation assessments prior to the start of each rebreathing procedure. You will be asked to 
look at a visual scale and describe your level of sedation from awake and alert to very sedated. An 
observer will also be documenting your sedation level prior to the start of each rebreathing procedure.  
 
Duffin Rebreathing 
 
You will have measurements of your breathing done at specified times during the study through a device 
that controls and measures the amount of oxygen and carbon dioxide you receive through a close-fitting 
face mask. This device in non-invasive.  
 
During the procedure you will be given instructions on how to breathe (deep breaths, quicker breaths, or 
normal breaths).  During screening you will be allowed to see the equipment to be used for the procedure 
and you will also be trained on the procedure by study staff so that you know what to expect and to see if 
you can tolerate it.    
 
The Duffin Rebreathing procedure will be overseen by study staff who have been fully trained on the 
procedure. You will be overseen by a study doctor for up to 6 hours after dosing. 
 
Eye Measurements 
 
You will have measurements of your eye done at specified times before and after the Duffin Rebreathing 
procedure by an automated device that takes a picture of your pupil and measures how it changes from a 
brief light stimulus. This is called pupillometry. The study staff will compare the changes in pupil 
measurements to the changes in breathing measurements. The device is held up to one of your eyes while 
the other eye is covered and then repeated on the same eye. The recording time on each eye takes less 
than 10 seconds and the procedure is painless.  
 
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 10 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
WHAT ARE YOUR RESTRICTIONS DURING THE STUDY? 
 
You will need to avoid the following while taking part in this study, and most importantly from the time 
of your screening visit until you check in:  
 
 
Restricted Item: 
Duration: 
Alcohol 
24 hours of check-in of all study periods. 
Caffeine or other xanthine containing products 
(for example, coffee, tea, cola or chocolate) 
24 hours of check-in of all study periods. 
Grapefruit 
24 hours of check-in of all study periods. 
Prescription medication 
14 days prior to dose until final check out. 
NSAIDs (Ibuprofen, Naproxen) 
14 days prior to dose until final check out. 
Complementary and alternative medicines 
28 days prior to first dose of study drug until final 
check out. 
Nicotine containing products 
6 weeks prior to screening until final check out. 
Participation in another clinical study of an 
investigational drug or treatment with an 
investigational drug. 
30 days prior to screening until final check out. 
You will receive a diet that does not contain any alcohol or caffeine. You must eat each meal that is 
served to you and eat at a reasonable pace (within 25 minutes).  
You will be required to fast for at least 8 hours prior to study drug administration. 
 
You may eat only meals and snacks that are provided to you during the periods of your stay. After 
checking out of the clinic, there are no dietary restrictions aside from what is listed in the table above.  
 
You must be willing to comply with study rules, including the meal schedule (25 minutes to eat), 
attempting to void at specified times (for example, before rebreathing assessment windows), remaining 
quiet, awake, undistracted, motionless, and seated during specified times, and avoiding vigorous exercise 
as directed throughout the duration of the study. Subjects will not be allowed to sleep during any 
rebreathing assessment periods. 
 
You must not have facial hair (be clean shaven) on all days when the Duffin Rebreathing procedure will 
be performed (including screening). 
 
Due to current precautions being taken for COVID-19, the following restrictions will be in place: 
 
• 
Subjects should be encouraged to wear masks except when in a private room without anyone else 
present or for a limited time for a study procedure (for example, study drug administration, 
switching to rebreathing mask) when instructed by study staff.  
• 
Subjects must practice social distancing, which will include having a maximum of 2 subjects per 
room for overnight stays and access to common areas will be per clinical research site standards. 
While subjects are in house, meals will be served per clinical research site standards. Subjects 
will spend most of their time in their rooms except for specified times for walking in the halls 
(with masks recommended). 
• 
Subjects must practice regular handwashing with soap and water, scrubbing hands for at least 20 
seconds or with approved hand sanitizer as supplied by study staff.  
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 11 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
If new information becomes available, there could be other precautions that lead to additional restrictions. 
 
On certain study days you may be required to get up very early (between 4 and 6 am) in order to complete 
study events. This will only be done when absolutely necessary and while it is important that you have 
sufficient rest during the study sometimes an early start to the day is unavoidable.   
 
ARE THERE RISKS TO YOU IF YOU ARE IN THIS STUDY? 
 
Please be advised that non-pharmacological (non-drug or medication) treatments (such as heating pack, 
stretches, hydration, etc.) are our first line of therapy for mild adverse events (side effects). The study 
doctor will be notified if a concomitant medication may be needed to treat an adverse event (AE). 
Following the protocol guidelines, the study doctor will assess your AE and develop a treatment plan. 
 
Risks are possible side effects of the study drug, the positive control medicine, and those of taking blood 
and other medical procedures: 
 
For Oxycodone 
• 
Abdominal effects – nausea, vomiting, constipation 
• 
Neurological effects – headache, insomnia (difficulty sleeping), asthenia (general weakness), 
lightheadedness, dizziness, drowsiness, agitation, anxiety, hallucinations, nightmares, somnolence 
(being sleepy) 
• 
Skin effects - itching 
• 
Less common, but serious adverse events include: 
o Lung effects -- respiratory depression/arrest (decreased/stopped breathing)  
o Heart/blood vessel effects –blood circulatory depression and hypotension (decreased 
blood pressure), cardiac arrest and/or shock (heart, lung, and circulatory changes that 
are potentially life threatening) 
 
For Paroxetine 
• 
Abdominal effects – nausea, diarrhea, vomiting, flatulence (passing gas), loss of appetite, dry 
mouth, constipation 
• 
Neurological effects – weakness, drowsiness, dizziness, anxiety, agitation, asthenia (general 
weakness), yawning, nervousness, tremors (shaking), insomnia (difficulty falling and/or staying 
asleep) 
• 
Eye effects - vision changes 
• 
Sexual effects - erectile dysfunction; delayed ejaculation; vaginal paresthesia (change in 
sensation), itching, and discharge; impotence; decreased libido (sex drive) 
• 
General effects – infection, sweating, hair loss 
 
For Escitalopram 
• 
Abdominal effects – Nausea, diarrhea, constipation, and indigestion  
• 
Neurological effects – Decreased libido (sexual desire), headache, and dizziness, drowsiness  
• 
General effects – Insomnia, ejaculation disorder, sweating increased, fatigue (feeling tired), 
somnolence (tiredness), impotence and anorgasmia (difficulty having an orgasm),  dry mouth, 
hair loss 
• 
Less common, but serious adverse events include: 
o Allergic reactions – Hypersensitivity reactions 
o Neurological effects – Syncope (fainting), seizures 
o Heart/blood vessel effects – QT interval prolongation (abnormal ECG), irregular 
heartbeat, abnormal blood clotting 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 12 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
o Abdominal effects – Increased liver enzymes (possible liver damage) 
o Serotonin syndrome (usually when prescribed with another serotoninergic [SSRI] 
medication which will not be done in this study – leads to fever, sweating, diarrhea and 
potential complications including seizures and muscle breakdown) 
 
For Ondansetron 
• 
Heart/blood vessel effects - hypoxia (decrease in oxygen to areas of the body) 
• 
Abdominal effects – diarrhea, constipation 
• 
Neurological effects – headache 
• 
General effects – fever, malaise (feeling of discomfort), fatigue (feeling tired) 
• 
Less common side effects include: 
o Allergic reactions – Hypersensitivity reactions including anaphylaxis and 
bronchospasm (difficulty breathing due to narrowing of the airways) (serious allergic 
reactions) 
o Heart/blood vessel effects: QT interval prolongation (abnormal ECG) and Torsade de 
Pointes (abnormal heart rhythm)  
o Serotonin syndrome (usually when prescribed with another serotoninergic [SSRI] 
medication which will not be done in this study – leads to fever, sweating, diarrhea 
and potential complications including seizures and muscle breakdown) 
 
You may be exposed to an additional drug that is used as a ‘rescue’ (reversing) medication. Naloxone 
may be administered if respiratory depression occurs following opioid administration. Side effects of this 
medication may include: 
 
For Naloxone 
• 
Heart/blood vessel effects – tachycardia (faster heart rate), hypertension (high blood pressure) 
• 
Lung effects - dyspnea (difficulty taking breaths) 
• 
Abdominal effects – nausea, vomiting, abdominal cramps 
• 
Neurological effects – trembling/shaking, seizures, restlessness, irritability, agitation 
• 
General effects – sweating, body aches, fever 
• 
Less common side effects include: 
o Ventricular tachycardia/fibrillation (Serious, abnormal heart rhythms) and pulmonary 
edema (accumulation of fluid in lungs) 
 
It is possible that you could experience a potentially serious irregularity in your heart rhythm 
during the study. For this reason, we will be monitoring your heart rhythm closely throughout the 
study, and we will have immediate medical care available for you if any problems occur. 
 
Problems or side effects that are not now known could also occur. You will be given any new information 
that may affect your willingness to start or continue in the study. 
 
The tests done at each visit are standard medical tests. The most unpleasant is often having blood samples 
taken. The risks of taking blood may include: 
• 
Fainting 
• 
Pain 
• 
Bruising 
• 
Rarely, there may be a small blood clot or infection at the site of the needle puncture 
 
The blood pressure cuff may also cause discomfort or bruising to the upper arm.  
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 13 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
In rare instances where a nurse, a doctor, or a technician, sustains an exposure to your blood, tissue, or 
body fluids by needle stick, cut or splash to mucosa or damaged skin, it may be necessary to test your 
blood, tissue, or body fluid sample for certain viral infections including Hepatitis B and C and HIV on the 
sample already available. This is to enable that person to receive appropriate counseling, monitoring and 
treatment if necessary. In this instance the study doctor or designee will offer you the information relevant 
to your health and advise you on the next steps. Confidentiality of your data will be respected at all times  
the state law. 
 
Risks or side effects associated with Duffin’s rebreathing procedure include: 
• 
Heart/blood vessel effects – rapid heart rate, increased blood pressure, chest pain 
• 
Lung effects – difficulty breathing 
• 
Neurological effects – headache, dizziness, confusion 
• 
Abdominal effects – nausea, vomiting 
• 
General effects – muscle twitches, fatigue (feeling tired), sweating 
 
Unknown Risks 
 
As with any drug, it is possible that you could experience an allergic reaction to the study drug used in 
this study. Symptoms of any allergic reaction can include: 
• 
Rash  
• 
Hives  
• 
Itching 
• 
Difficulty breathing 
• 
Closing of the throat  
• 
Swelling of the lips, tongue or face 
• 
Rarely, death. 
 
If you think you are having a severe allergic reaction, while outside the study center call 9-1-1 and 
seek medical attention immediately. 
 
It is very important that you tell the study doctor and the study staff about any side effects that you might 
experience. 
 
You may experience side effects or discomforts that are not listed on this form. Tell your study doctor or 
study staff immediately if you have any problems. Your safety will be closely monitored during the 
course of the study. 
 
For ECG Monitoring 
 
It is possible to be sensitive to the adhesives used on the electrodes that are applied to your chest when 
having an ECG performed. If this is the case, you could develop a temporary redness, irritation, or 
discoloration of the skin where the electrodes were applied. 
 
HIV, Hepatitis B and C, and COVID-19 Testing 
 
The risks of HIV and Hepatitis B and C testing include psychological and social risks. A positive test can 
lead to restrictions in freedom of travel to some countries and possible prejudices in job employment, 
insurance eligibility, housing and other forms of discrimination. Positive HIV, Hepatitis B and C, and 
COVID-19 test results must be reported to health authorities under state law. A positive HIV, Hepatitis B 
or C and/or COVID-19 result will exclude you from participation in the study. 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 14 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
Reproductive Risks 
 
The effects of the test drug on human pregnancy and the unborn child (fetus) are unknown. Therefore, it 
is very important that you do everything within your power not to become pregnant, or father a child 
during this study and for 2 months following the last dose. Please ensure that you follow the study birth 
control requirements outlined in the sections regarding information for male and female subjects above. 
 
If you become pregnant during the course of the study, you will be withdrawn from the study 
immediately. Neither Spaulding Clinical Research, LLC. nor the sponsor will be responsible for the cost 
of any obstetric or related care, or for your child's care. Female subjects are agreeing, by signing and 
dating this form, that information about your pregnancy and birth of your child may be collected. The 
information collected will include your health and the health of your unborn child during pregnancy, 
pregnancy outcome (miscarriage, termination, live birth, etc.), and the health of the baby after it is born 
(up to 6 weeks after delivery). 
 
Partners of male subjects who become pregnant will be asked to sign a separate consent form to allow 
collection of the information listed above. Your information will be kept confidential in accordance with 
state and HIPAA law. 
 
COVID-19 Risks 
 
Despite the extra precautions (for example, COVID-19 triage at screening/check-in, coronavirus testing, 
mandatory masks for study subjects and staff, social distancing including single-occupancy rooms, extra 
hand washing) that will be in place, there is still a risk of developing COVID-19 just as there is when you 
are not at Spaulding Clinical. Tell your study doctor or study staff about any new symptoms you develop 
during the study.  
 
The U.S. Centers for Disease Control and Prevention (CDC) currently highlights that people with the 
following symptoms may have COVID-19: 
• 
Cough 
• 
Shortness of breath or difficulty breathing 
• 
Fever or chills 
• 
Fatigue (feeling tired) 
• 
Muscle or body aches 
• 
Headache 
• 
Sore throat 
• 
New loss of taste or smell 
• 
Congestion or runny nose  
• 
Nausea or vomiting 
• 
Diarrhea 
 
It is important to note that COVID-19 can also present with other symptoms and just because you develop 
any of the above symptoms does not mean that you have COVID-19. Your study doctor will evaluate if 
your symptoms warrant further isolation from other study subjects/staff, additional coronavirus testing, 
and/or any treatment. 
 
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 15 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
NEW FINDINGS 
 
Your study doctor will tell you of any information learned during the course of the study that might cause 
you to change your mind about taking part in the study. You may contact the study doctor at any time 
after your participation ends to find out if any new information about this study has become available. 
 
 
WHAT IS THE ALTERNATIVE TO BEING IN THE STUDY? 
 
Since this is a study involving healthy subjects, your alternative is not to take part. 
 
WILL YOU BENEFIT FROM TAKING PART IN THE STUDY? 
 
You will not receive direct medical benefit from receiving the study drug. You may benefit by having 
your medical history recorded, undergoing a physical examination, and having blood and urine tests as 
they apply to this research project.    
 
Just by taking part in this research study, you may be helping future patients by providing important 
information about the study drug and by contributing to medical knowledge. 
 
 
WHO IS PAYING FOR THIS STUDY? 
 
The U.S. Food and Drug Administration is the Sponsor of the study.  
 
The U.S. Food and Drug Administration pays the study doctor to run this study. 
 
The study drug and all tests, procedures and visits required by the study are provided at no cost to you. 
The sponsor, the U.S. Food and Drug Administration pays for them. 
 
Information about this study is confidential. This information belongs to the U.S. Food and Drug 
Administration. We ask that you keep it private. You can discuss this information in private with your 
doctor or family to talk about your healthcare or to decide about taking part in this study. 
 
WILL YOU BE PAID FOR BEING IN THIS STUDY? 
 
Compensation for screening is as follows: 
 
• 
$170.00 if you qualify and take part in a study. $170.00 for your time and inconvenience if you 
do not qualify for a study. 
• 
If the results of the drug and alcohol tests are positive, or if you attempt to falsify your drug 
screen you will not receive any compensation. 
• 
If you screen for the study, qualify and are enrolled, your screening payment will be included in 
your first stipend payment. If you are not accepted into the study your screening payment will be 
processed and mailed within 7 calendar days of study enrollment. 
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 16 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
Compensation for this study is as follows: 
 
For subjects that complete the entire study (Day -1 to the Period 3 checkout (Day 106)), you will receive 
up to $31,000.00. This payment will be made in 4 separate payments as follows: 
 
• 
$8,833.00 will be paid after all check out procedures have been completed at the end of Period 1. 
• 
$8,833.00 will be paid after all check out procedures have been completed at the end of Period 2. 
• 
$8,834.00 will be paid after all check out procedures have been completed at the end of Period 3. 
• 
The remaining $4,500.00 will be paid after any additional follow up procedures are completed, 
and all results are reviewed. Once follow up procedures have been completed and accepted by 
study doctor, your final payment will be processed and mailed within 14 calendar days. 
 
 If you withdraw from the study early, you will only be paid for the visits you completed ($384.00 per 
visit day). 
 
NOTE: You may be required to return to the clinic for repeat blood test or other assessment (ECG, 
physical, vital signs) in between periods or after the final check out. This is considered part of the study 
and no additional compensation is available. Your final payment will not be released until all follow up 
procedures have been completed and accepted by the study doctor. Once follow up procedures have been 
completed and accepted by study doctor, your final payment will be processed and mailed within 14 
calendar days. 
 
NOTE: If you meet eligibility criteria you may be asked to be an alternate subject. Alternate subjects are 
eligible subjects that are in addition to the number of subjects in the event an enrolled subject drops out 
before their dose can take place or in the event it is not safe for a subject to move forward with dosing. If 
you are selected as an alternate subject and you agree to participate as an alternate subject, you may 
receive up to $250 if you are not needed to dose. If you are needed to replace a subject, you will be paid 
as stated for participating in and completing the study. If you agree to be an alternate subject, you will 
have all of the predose procedures as the enrolled subjects so that if you are needed, you will be ready to 
participate. If you are not needed, you will be discharged shortly after completion of the dosing round. 
 
No deductions for any state or federal withholding or any other similar taxes will be made and you are 
solely responsible for reporting such payments on your state and federal income tax returns.   
 
If you need to stay at Spaulding Clinical Research, LLC. for a longer period of time for safety reasons, 
you will be compensated at a rate proportional to the entire compensation for the study. 
 
If you are dismissed from the study for medical reasons OR if the study is temporarily or permanently 
halted, your compensation will be proportional to the time you spend in the study. 
 
If you are dismissed from the study because you have not complied with the instructions of the study 
staff, no compensation is available. Non-compliance includes, but is not limited to, improper conduct, 
taking alcohol and/or any drugs (including recreational drugs), tampering with the study drug, or 
consuming any foods/beverages not allowed in the study. 
Subjects may be reimbursed for travels expenses depending on need and Sponsor approval. 
 
By signing this consent, you expressly agree that you are an Independent Contractor for Spaulding 
Clinical Research, LLC. As an Independent Contractor, you will receive a 1099 form from Spaulding 
Clinical Research, LLC. The 1099 form shall document and report all payments and/or study stipends you 
received as an Independent Contractor for Spaulding Clinical Research, LLC.  In addition, because you 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 17 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
are an Independent Contractor and will be receiving payments and/or study stipends, those earnings are 
subject to wage garnishment.  If Spaulding Clinical receives an Earnings Garnishment Notice (or similar) 
from a State or Federal legal entity, we will adhere to that garnishment.   
 
COMPENSATION FOR INJURY 
 
It is important that you follow carefully all the instructions given by the study doctor and his/her study 
staff regarding this study.  
 
If you become ill or are physically injured as a result of participation in this study, please contact the 
study doctor right away at the telephone number listed on page one of this consent form. He/she will treat 
you or refer you for treatment. 
 
Spaulding Clinical Research, LLC. and/or its affiliated institutions has not set aside funds to provide you 
with financial compensation or reimbursement for the cost of care provided to treat a research-related 
injury or for other expenses arising from a research-related injury. You or your insurer will be responsible 
for the payment of any medical treatments for research related injuries or illness. By signing and dating 
this consent form, you are not giving up any legal rights. If this research study is conducted in a negligent 
manner and you are injured as a direct result, you may be able to recover the costs of care and other 
damages from the individuals or organizations responsible for your injury as you still have the right to 
seek compensation for injury related to malpractice, negligence, fault, guilt or blame of those involved in 
the research. 
 
PROTECTING THE PRIVACY OF YOUR HEALTH DATA 
 
Unless required by law, your name will not be disclosed outside the research clinic. Your name will be 
available only to the following people or agencies: the study doctor and study staff; and authorized 
representatives of the study doctor; Advarra Institutional Review Board, health authority inspectors, such 
as the U.S. Food & Drug Administration and the European Medicines Agency; study monitors and 
auditors; and authorized Clinical Research Organization representatives. The above mentioned 
individuals will use the personal information collected as part of this study, including your medical 
records (“study information”) to check that the study is conducted correctly and to ensure the accuracy of 
the study information. These people are all obligated to maintain confidentiality by the nature of their 
work, or are bound by confidentiality agreements. If required, the study doctor may contact your personal 
doctor to collect additional medical information and your past medical history. 
 
The study doctor may only share your study information with people whom you have permitted to see it. 
However once your study information is shared as authorized, it may no longer be protected by federal 
law and may be re-disclosed without your permission. 
 
While participating in this study, the study doctor will replace your name with a special code that 
identifies you. This code, along with your study information, will be used by the U.S. Food and Drug 
Administration and their representatives, for the study purposes mentioned above and to help establish 
whether the study drug is safe and effective. Any data and/or biospecimens provided to the U.S. Food and 
Drug Administration will be coded (stripped of identifiers such as name, address, or account number) and 
the key allowing the code to be linked to your personal information will be kept by the study team and 
never released to the agency. Therefore, the U.S. Food and Drug Administration will not be able to re-
identify you. The U.S. Food and Drug Administration may share your coded information, as necessary, 
with the U.S. Food and Drug Administration affiliates who work within the scope of this consent;  


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 18 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
Advarra IRB and Regulatory agencies such as the National Health Authorities, and the European 
Medicines Agency. 
 
You should be aware that some countries may not offer the same level of privacy protection as you are 
used to in the country where you live or where this study is conducted. However, the U.S. Food and Drug 
Administration will keep any information it receives to the same standard of confidentiality as far as 
permitted by applicable local law. The U.S. Food and Drug Administration  has also entered into 
agreements with third parties working for the U.S. Food and Drug Administration to secure adequate 
protection of your data and samples.  
 
The study information will be kept confidential within the limits of the law.. The U.S. Food and Drug 
Administration may keep study samples and data collected for future research. Identifiers will be removed 
from your identifiable private information or identifiable biospecimens collected during this  study so that 
data cannot be linked to you. The coded data and/or biospecimen could then be used for future research 
studies or distributed to another investigator for future research studies without additional informed 
consent .You will not be contacted about each of these future uses for additional informed consent. No 
additional participation time or procedures will be required beyond what is described above for the 
primary study. The coded data from the study will be replaced with a unique identifier and may be 
released to a data warehouse (location that will store the data) or used as part of a publication. It may be 
shared broadly for research purposes outside of the U.S. Food and Drug Administration and Spaulding 
Clinical Research, LLC. Other investigators study doctors will have access to limited clinical and 
biological data such as age, gender, and disease status. Your samples will only be used for research 
purposes. It is also possible that your samples and data will never be used. Results of research done on 
your samples and data will not be available to your personal doctor. If the results of this study are 
published or presented in a meeting, you will not be named and nobody will be able to tell that you were 
in the study from the publication or presentation. 
 
WHO CAN YOU CONTACT FOR MORE INFORMATION ABOUT THIS STUDY? 
 
You can ask questions about this consent form or the study (before you decide to start the study, at any 
time during the study, or after completion of the study). Questions may include: 
 
Who to contact in the case of a research-related injury or illness; 
• 
Payment or compensation for being in the study, if any; 
• 
Your responsibilities as a study subject; 
• 
Eligibility to participate in the research; 
• 
The study doctor’s or study site’s decision to exclude you from participation; 
• 
Results of tests and/or procedures; 
• 
Other questions, concerns, or complaints. 
 
Contact the study doctor or study staff listed on the first page of this form with any questions, concerns 
or complaints.   
 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 19 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
WHOM TO CONTACT ABOUT THIS STUDY 
 
During the study, if you experience any medical problems, suffer a research-related injury, or have 
questions, concerns or complaints about the study such as: 
 
• 
Whom to contact in the case of a research-related injury or illness; 
• 
Payment or compensation for being in the study, if any; 
• 
Your responsibilities as a research subject; 
• 
Eligibility to participate in the study; 
• 
The study doctor’s or study site’s decision to exclude you from participation; 
• 
Results of tests and/or procedures; 
 
Please contact the study doctor at the telephone number listed on the first page of this consent 
document.  
 
If you seek emergency care, or hospitalization is required, alert the treating physician that you are 
participating in this research study.  
 
An institutional review board (IRB) is an independent committee established to help protect the rights of 
research subjects. If you have any questions about your rights as a research subject, contact: 
 
• 
By mail: 
Study Subject Adviser 
Advarra IRB 
6100 Merriweather Dr., Suite 600 
Columbia, MD 21044 
• 
or call toll free:    877-992-4724 
• 
or by email:          adviser@advarra.com 
 
Please reference the following number when contacting the Study Subject Adviser: Pro00064533. 
 
An IRB is a group of people who review research studies to protect the rights and welfare of research 
subjects.   
 
IS YOUR PARTICIPATION VOLUNTARY? 
 
Yes, your participation in this study is strictly voluntary. You may refuse to take part in it, or you may 
stop participating at any time, even after signing this informed consent. There will be no penalty or loss of 
benefits to which you are otherwise entitled. However, if you decide to leave the study before it ends, the 
study doctor will need to see you before you are released from the study. 
 
The study doctor may also decide to remove you from the study at any time without your consent. The 
study doctor may choose to take you out of the study because of unexpected or serious side effects, or for 
other scientific, technical, or safety considerations. 
 
Examples why you may be taken out of the study are: 
• 
Staying in the study would be harmful 
• 
You need treatment not allowed in this study 
• 
You failed to follow instructions 
• 
You become pregnant 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 20 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
• 
The study is cancelled 
• 
Your study treatment arm is stopped 
If your participation ends for any reason, you will return to the study for the following study procedures: 
• 
Physical examination. 
• 
Pregnancy test (if necessary). 
• 
Body weight and body temperature. 
• 
Blood pressure and pulse rate. 
• 
Pulse oximetry (measurement of blood oxygen levels) 
• 
ECG. 
• 
Blood draws for hematology and chemistry. 
• 
Blood draws for PK. 
• 
Urine will be collected for urinalysis. 
• 
Assessment for adverse events and concomitant medications (if you are taking any medications at 
the same time you were participating in the study) 
If you should decide to leave the study you should tell the study doctor or study staff. They will make 
sure that proper procedures are followed and a final visit is made for your safety. 
A description of this clinical trial will be available on http://www.ClinicalTrials.gov, as required by U.S. 
Law. This Web site will not include information that can identify you. At most, the Web site will include 
a summary of the results. You can search this Web site at any time. 
 
STATEMENT OF CONSENT  
 
I have read this form and its contents were explained to me. I agree to be in this research study for the 
purposes listed above. All of my questions were answered to my satisfaction. I will receive a signed and 
dated copy of this form for my records.  I am not giving up any of my legal rights by signing this form.   
 
___________________________________ 
 
____/____/____ 
Signature of Research Subject 
 
Date 
 
___________________________________ 
 
 
 
 
_______________ 
Printed Name of Research Subject 
 
 
 
 
 
Time (24hr) 
 
STATEMENT OF PERSON OBTAINING INFORMED CONSENT  
 
I have carefully explained to the subject the nature and purpose of the above study. There has been an 
opportunity for the subject to ask questions about this research study. I have been available to answer any 
questions that the subject has about this study. 
 
                                                                                
 
____/____/____ 
Initials of Person Obtaining Informed Consent 
 
Date 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 21 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
HIPAA Authorization Agreement 
Permission to Review, Use and Release Information about You  
 
If you decide to be in this study, the study doctor and research team will use and share health data about 
you to conduct the study. Health data may include: 
 
• 
Your name. 
• 
Address. 
• 
Phone number. 
• 
Date of birth. 
• 
Medical history. 
• 
Information from your study visits, including all test results.   
 
Health data may come from your study records or from existing records kept by your doctor or other 
health care workers.   
 
For this study, the research team may share health data about you with authorized users. Authorized users 
may include: 
 
• 
Representatives of the U.S. Food and Drug Administration (such as representatives who may 
audit the research or receive reports of adverse events). 
• 
Representatives of Spaulding Clinical Research, LLC. 
• 
Representatives of Advarra IRB. (an Institutional Review Board that reviews this study)  
• 
Other U.S. governmental agencies. 
• 
Government agencies to whom certain diseases (like HIV, hepatitis, and STIs) must be reported. 
• 
Governmental agencies of other countries. 
• 
Labs working with the sponsor on this study. 
• 
Other authorized users. 
 
The U.S. Food and Drug Administration and those working for the U.S. Food and Drug Administration 
may use the coded health data sent to them: 
 
• 
To see if the study drug works and is safe. 
• 
To compare the study drug to other drugs. 
• 
For other research activities related to the study drug. 
 
Once your health data has been shared with authorized users, it may no longer be protected by federal 
privacy laws.   
 
Your permission to use and share health data about you will not end unless required by state law. If state 
law applies, your permission to use and share health data about you will end on December 31, 2060.  
 
You may take back your permission to use and share health data about you at any time by writing to the 
study doctor. If you do this, you will not be able to stay in this study. No new health data that identifies 
you will be gathered after your written request is received. However, health data about you that has 
already been gathered may still be used and given to others as described in this form.   
 
Your right to access your health data in the study records will be suspended during the study to keep from 
changing the study results. When the study is over, you can access your study health data. 


U.S. Food and Drug Administration / Protocol Number SCR-012  
Page 22 of 22  
 
Jan Matousek, D.O. 
Advarra IRB Approved Version 30 Mar 2023 
 
 
 
If you decide not to sign this form, you will not be able to take part in the study. 
 
STATEMENT OF AUTHORIZATION 
 
I have read this form and its contents were explained. My questions have been answered. I voluntarily 
agree to allow study staff to collect, use and share my health data as specified in this form. I will receive a 
signed and dated copy of this form for my records. I am not giving up any of my legal rights by signing 
this form.   
 
 
 
 
 
____/____/____ 
Signature of Research Subject 
 
 
Date 
 
___________________________________ 
 
 
 
Printed Name of Research Subject 
 
 
 
 
 
 
STATEMENT OF PERSON OBTAINING AUTHORIZATION 
 
I have carefully explained to the subject the nature and purpose of this form. I have been available to 
answer any questions that the subject has about this form. 
 
                                                                        
 
 
____/____/____ 
Initials of Person Obtaining Authorization 
 
 
Date 
 
 
 
 
 
 
 

Prot_000.pdf: 
Study Title: Clinical Study to investigate the effect of administration of selective 
serotonin reuptake inhibitors and an opioid on ventilation 
 
Document Title: Clinical Study Protocol – Study No. SCR-012 
 
Document Date: 21 July 2022 
 
NCT Number: NCT05470465 


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CLINICAL STUDY PROTOCOL 
 Clinical study to investigate the effect of administration of selective 
serotonin reuptake inhibitors and an opioid on ventilation 
 
PROTOCOL NO. SCR-012 
 
Sponsor: 
U.S. Food and Drug Administration 
White Oak Building #64, Room 2072 
10903 New Hampshire Avenue 
Silver Spring, MD 20993 
 
Sponsor Study Lead: 
David Strauss, MD, PhD 
Director, Division of Applied Regulatory Science  
U.S. Food and Drug Administration 
Telephone: 301-796-6323 
Email: david.strauss@fda.hhs.gov 
 
 
Sponsor Medical 
Monitor: 
Keith Burkhart, MD 
U.S. Food and Drug Administration 
301-796-2226 
Email: keith.burkhart@fda.hhs.gov 
 
 
Project Manager: 
Jeffry Florian, PhD  
U.S. Food and Drug Administration  
Telephone: 301-796-4847  
Email: jeffry.florian@fda.hhs.gov 
 
 
 
Version of Protocol: 
1.1 
 
Date of Protocol: 
21 July 2022 
 
CONFIDENTIAL 
The concepts and information contained in this document or generated during the study 
are considered proprietary and may not be disclosed in whole or in part without the 
expressed written consent of the U.S. Food and Drug Administration. 
 
 


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SPONSOR SIGNATURE PAGE
This study will be conducted with the highest respect for the individual participants in 
accordance with the requirements of this clinical study protocol and also in accordance 
with the following:
x The ethical principles that have their origin in the Declaration of Helsinki;
x International Council for Harmonisation (ICH) harmonised tripartite guideline E6 
(R2): Good Clinical Practice; and
x All applicable laws and regulations, including without limitation, data privacy laws 
and compliance with appropriate regulations, including human subject research 
requirements set forth by the Institutional Review Board (IRB).
David Strauss, MD, PhD
Director, Division of Applied 
Regulatory Science 
U.S. Food and Drug Administration
Date



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Protocol Number: SCR-012
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INVESTIGATOR SIGNATURE PAGE
I confirm that I have read and that I understand this protocol, the investigator brochure, 
and other product information provided by the sponsor. I agree to conduct this study in 
accordance with the requirements of this protocol and also protect the rights, safety, 
privacy, and well-being of study subjects in accordance with the following:
x
The ethical principles that have their origin in the Declaration of Helsinki;
x
ICH harmonised tripartite guideline E6 (R2): Good Clinical Practice;
x
All applicable laws and regulations, including without limitation data privacy laws 
and regulations;
x
Human subject research requirements set forth by the IRB;
x
Regulatory requirements for reporting of serious adverse events (SAEs) defined in 
Section 4.7.3.1 of this protocol; and
x
Terms outlined in the Clinical Study Site Agreement.
I further authorize that my personal information may be processed and transferred in 
accordance with the uses contemplated in Section 6 of this protocol.
Jan Matousek, D.O.
Principal Investigator
Date



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Protocol Number: SCR-012 
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TABLE OF CONTENTS 
PROTOCOL SYNOPSIS ............................................................................................................................ 7 
1. INTRODUCTION ............................................................................................................................... 22 
2. STUDY OBJECTIVES .......................................................................................................................... 23 
2.1 PRIMARY OBJECTIVES .............................................................................................................................. 23 
2.2 SECONDARY OBJECTIVES ........................................................................................................................... 23 
2.3 EXPLORATORY OBJECTIVES ........................................................................................................................ 24 
3. STUDY ENDPOINTS .......................................................................................................................... 24 
3.1 PRIMARY ENDPOINTS ............................................................................................................................... 24 
3.2 SECONDARY ENDPOINTS ........................................................................................................................... 24 
3.3 EXPLORATORY ENDPOINTS ........................................................................................................................ 24 
4. INVESTIGATIONAL PLAN .................................................................................................................. 26 
4.1 STUDY DESIGN ....................................................................................................................................... 26 
4.1.1 Risk/Benefit ................................................................................................................................ 27 
4.2 SELECTION OF STUDY POPULATION ............................................................................................................. 30 
4.2.1 Inclusion Criteria ........................................................................................................................ 30 
4.2.2 Exclusion Criteria ........................................................................................................................ 31 
4.3 SCREENING FAILURES ............................................................................................................................... 33 
4.4 TERMINATION OF STUDY OR INVESTIGATIONAL SITE ....................................................................................... 34 
4.4.1 Criteria for Termination of the Study ......................................................................................... 34 
4.4.2 Criteria for Termination of the Investigational Site .................................................................... 34 
4.5 CRITERIA FOR SUBJECT WITHDRAWAL ......................................................................................................... 34 
4.5.1 Handling of Withdrawals ........................................................................................................... 35 
4.5.2 Replacement of Subjects ............................................................................................................ 35 
4.6 STUDY VISITS ......................................................................................................................................... 36 
4.6.1 Recruitment ................................................................................................................................ 36 
4.6.2 Compensation ............................................................................................................................ 36 
4.6.3 Screening .................................................................................................................................... 36 
4.6.4 Study Periods .............................................................................................................................. 37 
4.7 STUDY PROCEDURES ................................................................................................................................ 40 
4.7.1 Pharmacokinetic Assessments ................................................................................................... 40 
4.7.2 Pharmacodynamic Assessments ................................................................................................ 41 
4.7.3 Safety Assessments .................................................................................................................... 44 
4.7.4 Demographics and Medical History ........................................................................................... 48 
4.8 STUDY TREATMENTS ................................................................................................................................ 49 
4.8.1 Dose Strategy ............................................................................................................................. 49 
4.8.2 Treatments Administered ........................................................................................................... 49 
4.8.3 Dose Selection and Schedule ...................................................................................................... 50 
4.8.4 Method of Assigning Subjects to Treatment Sequence .............................................................. 51 
4.8.5 Identity of Study Drugs ............................................................................................................... 52 
4.8.6 Management of Clinical Supplies ............................................................................................... 53 
4.8.7 Blinding ...................................................................................................................................... 54 
4.8.8 Treatment Compliance ............................................................................................................... 55 
4.8.9 Prior and Concomitant Medications .......................................................................................... 55 
4.8.10 Subject Restrictions .................................................................................................................. 55 


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4.9 STATISTICAL METHODS ............................................................................................................................ 56 
4.9.1 Sample Size ................................................................................................................................ 56 
4.9.2 Analysis Populations .................................................................................................................. 57 
4.9.3 General Statistical Considerations ............................................................................................. 57 
4.9.4 Subject Disposition ..................................................................................................................... 57 
4.9.5 Demographics and Baseline Characteristics .............................................................................. 58 
4.9.6 Rebreathing Analyses ................................................................................................................. 58 
4.9.7 Pharmacokinetic Analysis .......................................................................................................... 59 
4.9.8 PK/PD Modeling ......................................................................................................................... 59 
4.9.9 Electrocardiogram Analyses ....................................................................................................... 60 
4.9.10 Additional Analyses .................................................................................................................. 60 
4.9.11 Safety Analyses ........................................................................................................................ 62 
4.9.12 Interim Analyses ....................................................................................................................... 63 
4.9.13 Missing Data ............................................................................................................................ 63 
4.10 DATA QUALITY ASSURANCE .................................................................................................................... 63 
4.11 DATA SHARING ..................................................................................................................................... 63 
5. ETHICAL CONSIDERATIONS .............................................................................................................. 64 
5.1 ETHICAL CONDUCT OF THE STUDY .............................................................................................................. 64 
5.2 INSTITUTIONAL REVIEW BOARD (IRB) ......................................................................................................... 64 
6. ADMINISTRATIVE PROCEDURES ....................................................................................................... 64 
6.1 RESPONSIBILITIES OF THE INVESTIGATOR ...................................................................................................... 64 
6.1.1 Form FDA 1572 ........................................................................................................................... 64 
6.1.2 Adherence to Protocol ................................................................................................................ 65 
6.1.3 Reporting Requirements ............................................................................................................ 65 
6.1.4 Source Documentation ............................................................................................................... 65 
6.1.5 Retention of Records .................................................................................................................. 65 
6.1.6 Financial Disclosure and Obligations ......................................................................................... 65 
6.2 CONFIDENTIALITY AND DISCLOSURE OF DATA ............................................................................................... 66 
6.3 SUBJECT CONSENT .................................................................................................................................. 66 
6.4 DATA COLLECTION .................................................................................................................................. 67 
6.5 PUBLICATIONS ........................................................................................................................................ 67 
7. STUDY MANAGEMENT ..................................................................................................................... 67 
7.1 MONITORING ......................................................................................................................................... 67 
7.2 MANAGEMENT OF PROTOCOL AMENDMENTS AND DEVIATIONS ....................................................................... 68 
7.2.1 Modification of the Protocol ...................................................................................................... 68 
7.2.2 Protocol Violations and Deviations ............................................................................................ 68 
REFERENCE LIST ................................................................................................................................... 70 
8. APPENDICES .................................................................................................................................... 76 
APPENDIX A – SCHEDULE OF EVENTS ................................................................................................................ 76 
APPENDIX B – LIST OF ABBREVIATIONS ............................................................................................................. 77 
APPENDIX C – PROTOCOL REVISION HISTORY ..................................................................................................... 79 
 
 
 


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LIST OF TABLES 
TABLE 4-1: STUDY SCHEDULE .............................................................................................................................. 26 
TABLE 4-2: STUDY TREATMENT GROUPS ............................................................................................................... 26 
TABLE 4-3: CLINICAL LABORATORY TESTS & DIAGNOSTIC SCREENING TESTS ................................................................. 47 
 
 
 
 
 
 
 
 
 
 


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PROTOCOL SYNOPSIS 
Protocol Number: 
SCR-012 
Title: 
Clinical study to investigate the effect of selective serotonin reuptake 
inhibitors and an opioid on ventilation 
Investigators: 
Principal Investigator: Jan Matousek 
Study Physician: Jan Matousek 
Study Phase: 
1 
Study Period: 
This is a 3-period, double-blind, randomized crossover study. The 
duration of each treatment period will be 21 days in addition to a three-
week washout between periods. The duration of study participation will 
be 106 days (excluding the screening period). 
Study Site: 
Spaulding Clinical Research Unit, West Bend, Wisconsin 
Background and 
Motivation: 
A well-known and potentially fatal adverse reaction associated with 
opioid administration, particularly in the scenario of misuse, abuse, or 
when coadministered with certain other drugs is that people ‘stop 
breathing’. Research suggests this is caused by a reduced ventilatory 
response to increasing levels of carbon dioxide. In August 2016, the 
U.S. Food and Drug Administration (FDA) included boxed warnings 
about increased potential for respiratory depression with co-use of 
benzodiazepines and opioids.1 In response to this action, concerns were 
raised because patients may be prescribed other psychotropic drugs that 
may have similar adverse reactions when combined with opioids. 
Subsequently, FDA performed a review of the literature and identified 
13 psychotropic drugs for evaluation in an in vivo animal study (using a 
rat model). The in vivo study identified 4 drugs that had significant 
effects when combined with oxycodone on arterial carbon dioxide.2 
Two drugs (quetiapine and paroxetine) were selected for further 
evaluation in a human clinical study evaluating drug effects on 
hypercapnic ventilation.  
To study the effects of opioids alone or in combination with other 
psychotropic drugs on ventilation, FDA used a procedure referred to as 
Read rebreathing.3-4 With Read rebreathing, study participants rebreathe 
through a circuit with increased levels of O2 and CO2 . The artificially 
increased levels of CO2 trigger the subjects to increase ventilation. This 
“hypercapnic ventilatory response” can be decreased by opioids, 
benzodiazepines, and other drugs.5-19 
The previous study, which included 5-days of study drug dosing with 
oxycodone administered on day 1 or 5 showed quetiapine co-


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administered with oxycodone did not cause a significant decrease in 
hypercapnic ventilation compared to oxycodone alone.20 In contrast, 
paroxetine caused a decrease in hypercapnic ventilation compared to 
oxycodone alone, and an additive effect was seen when combined with 
oxycodone. This mechanism is due to a direct pharmacodynamic effect, 
rather than a pharmacokinetic interaction and most likely due to its 
serotonergic properties. Paroxetine is highly selective for inhibiting the 
serotonin transporter versus other monoamine transporters and other 
receptors in general.21-22 Although different types of serotonergic 
receptors and neurons can have differential effects on breathing, 
paroxetine does not bind to serotonin receptors at clinically-relevant 
therapeutic exposures.23-24 In addition, nonclinical and clinical studies 
have shown different SSRIs can have independent effects on ventilation, 
though SSRIs have not been shown to cause severe respiratory 
depression on their own.25-43 This supports the need for additional 
investigation on the effects of serotonergic drugs.  
The previous study evaluated effects on ventilation over 5-days of 
dosing. SSRIs take approximately 3 weeks to reach maximal therapeutic 
effect there, which correlates with the time required for pre-synaptic 
inhibitory serotonergic receptors to desensitize.44-46 Drug-effects on 
ventilation should be evaluated for a similar time period to confirm if 
effects persist under steady state conditions 
As part of this proposed study with a longer dosing duration and 
different SSRIs, hypercapnic ventilation will be assessed under 
hyperoxic and hypoxic gas levels using a modified Read rebreathing 
approach referred to as Duffin rebreathing. These modifications allow 
for critical physiological measurements and thresholds to be captured 
that can then be used to model the effects of drugs when there are 
dynamic changes in PO2 and PCO2, such as during a real-world opioid 
overdose.47-52  
Objectives and 
Endpoints: 
The objectives of this study are: 
Primary Objectives 
Primary objectives include the following: 
x To study ventilatory effects of SSRIs (paroxetine or 
escitalopram) combined with oxycodone compared to 
oxycodone alone after 21 days of SSRI dosing 
x To study ventilatory effects of SSRIs (paroxetine or 
escitalopram) compared to placebo after 20 days of SSRI dosing  
 
Secondary Objectives 
Secondary objectives include the following: 


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x To compare ventilatory effects of SSRIs (paroxetine or 
escitalopram) combined with oxycodone compared to 
oxycodone alone after 6 and 12 days of SSRI dosing 
x To compare ventilatory effects of SSRIs (paroxetine or 
escitalopram) compared to placebo after 5 and 11 days of SSRI 
dosing 
 
Exploratory Objectives 
x To study whether paroxetine or escitalopram affects the 
pharmacokinetics of oxycodone 
x To evaluate differences in hypercapnic ventilatory response 
under hyperoxic or hypoxic rebreathing  
x To study whether there is a direct pharmacodynamic interaction 
between paroxetine or escitalopram and oxycodone 
x To summarize additional pharmacokinetic parameters and 
pharmacodynamic measurements collected during the study 
The endpoints for this study are: 
Primary Endpoint 
x Minute ventilation at the 55mm Hg end tidal CO2 point (VE55) 
under hyperoxic conditions on day 21  
x VE55 under hyperoxic conditions on day 20 
 
Secondary Endpoints 
Secondary endpoints include the following: 
x VE55 under hyperoxic conditions on days 6 and 12 
x VE55 under hyperoxic conditions on days 5 and 11 
 
Exploratory Endpoints 
x The maximum observed plasma concentration (Cmax) and area 
under the plasma concentration time curve (AUC) of oxycodone 
and oxymorphone on days 6, 12, and 21  
x Baseline minute ventilation, ventilatory recruitment threshold, 
slope of the minute ventilation / end-tidal partial pressure of 
carbon dioxide (end-tidal PCO2) regression line, and 
extrapolated ventilatory recruitment threshold collected during 
hyperoxic and hypoxic rebreathing 
x The PK/PD relationship for study drugs when administered 
alone or in combination with oxycodone 
x Additional pharmacokinetic and pharmacodynamic (e.g., 
ventilation, pupillometry, ECG) endpoints as specified in the 
protocol 
 


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Study Design: 
This study will be a randomized, double blind, three period crossover 
study with approximately 25 healthy volunteer participants. This study 
will include three 21-day treatment periods with a 3-week washout 
between each period. Each subject will be randomized to 1 of 6 
treatment sequences (i.e., ABC, ACB, BAC, BCA, CAB, CBA). FDA 
will prepare the randomization schedule. 
Study Schedule: 
 
Study Treatments: 
 
 
 
Subjects will report to the study site for screening from Days -28 to -2. 
During the screening visit, the inclusion and exclusion criteria will be 
reviewed to ensure the subject is appropriate for the study. The informed 
consent form will be reviewed with the subject by a member of the 
study team and the subject will be encouraged to ask questions to ensure 
he or she has a good understanding of the study. If the subject is eligible 
and agrees to participate, the subject will be asked to sign the informed 
consent form before any study-specific procedure is performed, 
including randomization. 
After the consent process is complete, demographic data, medical 
history, and concomitant medications will be recorded. A physical 
examination will be performed by a study team member. Clinical 
laboratory tests (hematology, seum chemistry, and urinalysis) will be 
performed. Female subjects must have a negative pregnancy test result. 
Screening tests will be performed within 28 days of and no later than 2 
days before Day 1. 
At check-in for the first period (Day -1), eligibility criteria will be 
reviewed, any changes in medical history (including concomitant 
medications) will be documented. At check-in for all periods, vital sign 
Day -1  
Days 1-21 
Days 22-42 
Days 42-63 
Days 64-84  
Days 85-105 
Day 
106 
Check-
in  
Period 1 
Washout 
Period 2  
Washout  
Period 3  
Check-
out 
Treatment 
Day 
1-5 
6 
7-11 
12 
13-20 
21 
A 
Placebo QD 
Placebo + 
10 mg 
oxycodone 
Placebo QD 
Placebo +  
10 mg 
oxycodone 
Placebo QD 
Placebo  + 
10 mg 
oxycodone 
B 
40 mg 
paroxetine QD 
40 mg 
paroxetine + 
10 mg 
oxycodone 
60 mg 
paroxetine QD 
60 mg 
paroxetine + 
10 mg 
oxycodone 
60 mg 
paroxetine QD 
60 mg 
paroxetine + 
10 mg 
oxycodone 
C 
20 mg 
escitalopram 
QD 
20 mg 
escitalopram +  
10 mg 
oxycodone 
30 mg 
escitalopram 
QD 
30 mg 
escitalopram +  
10 mg 
oxycodone 
30 mg 
escitalopram 
QD 
30 mg 
escitalopram + 
10 mg 
oxycodone 


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measurements, and a 12-lead electrocardiogram (ECG) will be 
performed. In addition, clinical laboratory, drug, alcohol, two 
rebreathing assessments (one hyperoxic and one hypoxic), and a 
COVID-19 rapid antigen. An intravenous (IV) catheter may be inserted 
into the subject’s forearm region for blood collection (if needed).  
Participants will enter the clinic on a staggered basis in cohorts of 
approximately five so that no more than five subjects are undergoing 
rebreathing on any given day. Subjects will be staggered to allow for 
direct safety overview by medical staff during Duffin’s rebreathing.  
Participants will receive either placebo, paroxetine, or escitalopram on 
days 1-21 for each period. Oxycodone will be administered on days 6, 
12, and 21 of each period. Dosing of the study drugs will occur at time 0 
on each day. Oxycodone dosing will be at 3 h so that maximum 
concentration occurs for all drugs is at approximately the same time.   
Participants will be confined to the study clinic from day -1 until the 
first day of each washout period. There will be a three-week washout 
between each period. Subjects will be discharged from the study after 
completion of all study procedures. If a subject discontinues from the 
study prematurely, all procedures scheduled for the end of the study will 
be performed. Meal timing and components, activity levels, and general 
conditions in the study clinic will be as similar as possible on the 
treatment days. 
Upon return to clinic, on Days 42 & 84, eligibility criteria to continue 
study participation will be reviewed (see Schedule of Events for criteria 
listed on Days 42 & 84), any changes in medical history (including 
concomitant medications) will be documented. 
Subject Population: 
Approximately 25 healthy participants are planned for enrollment. 
Every effort will be made to maintain an approximate 50:50 male-to-
female sex distribution.  
Study and 
Reference Drugs, 
Dosage, and Route 
of Administration: 
For all drugs, standard drug doses or doses used in prior studies in 
healthy participants will be used in this study. Multiple doses of the 
assigned study drug will be administered to each subject during the 
treatment period. Oxycodone, paroxetine, escitalopram, ondansetron, 
and placebo will be administered orally. Subjects will complete each of 
the three treatments (A, B, and C) and will receive the following drugs 
alone or in combination:  
x Oxycodone 10 mg QD (2 x 5 mg tablets) on days 6, 12, and 21 
in each treatment (A-C)  
x Paroxetine 40 mg QD (2 x 20 mg tablet) on days 1-6 and 60 mg 
QD (3 x 20 mg tablets) on days 7-21 in treatment B 


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x Escitalopram 20 mg QD (2 x 10 mg tablet) on days 1-6 and 30 
mg QD (3 x 10 mg tablets) on days 7-21 in treatment C 
x Matching oral placebo for paroxetine and escitalopram 
x Participants will also receive ondansetron 4 mg orally 30 min 
before oxycodone administration 
Inclusion Criteria: 
Subjects who meet all the following inclusion criteria will be eligible to 
participate in the study:  
1. Subject signs an IRB approved written informed consent and 
privacy language as per national regulations (e.g., Health Insurance 
Portability and Accountability Act authorization) before any study 
related procedures are performed.  
2. Subject is a healthy, non-smoking man or woman, 18 to 50 years 
of age, inclusive, who has a body mass index of 18.5 to 33.0 
kg/m2, inclusive, at Screening. 
3. Subject has normal medical history findings, clinical laboratory 
results, vital sign measurements, pulse oximetry, 12-lead ECG 
results, and physical examination findings at screening or, if 
abnormal, the abnormality is not considered clinically significant 
(as determined and documented by the investigator or designee). 
4. Subject must have a negative test result for alcohol and drugs of 
abuse at screening and check-in days.  
5. Subject must test negative for severe acute respiratory syndrome 
corona virus 2 (SARS-CoV-2) by a rapid antigen test at check-in 
for all study periods. If a subject’s test comes back as invalid, the 
test can be repeated. 
6. Female subjects must be of non-childbearing potential (confirmed 
with follicle-stimulating hormone levels > 40 mIU/mL)  or, if they 
are of childbearing potential, they must: 1) have been strictly 
abstinent for 1 month before check-in (Day -1) and agree to remain 
strictly abstinent for the duration of the study and for at least 
1month after the last application of study drug; OR 2) be practicing 
2 highly effective methods of birth control (as determined by the 
investigator or designee; one of the methods must be a barrier 
technique) from at least 1 month before check-in (Day -1) until at 
least 1 month after the end of the study.  
7. Male subjects must agree to practice 2 highly effective methods of 
birth control (as determined by the investigator or designee) from 
at least 1 month before check-in (Day -1) until at least 1 month 
after the last dose of study drug. 
8. Subject is highly likely (as determined by the investigator) to 
comply with the protocol defined procedures and to complete the 
study. 
Exclusion Criteria: 
Subjects who meet any of the following exclusion criteria will not be 
eligible to participate in the study: 


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1. Subject has used any prescription or nonprescription drugs 
(including aspirin or NSAIDs and excluding oral contraceptives and 
acetaminophen) within 14 days or 5 half-lives (whichever is longer) 
or complementary and alternative medicines within 28 days before 
the first dose of study drug. This includes prescription or 
nonprescription ophthalmic drugs. 
2. Subject is currently participating in another clinical study of an 
investigational drug or has been treated with any investigational 
drug within 30 days or 5 half-lives (whichever is longer) of the 
compound. 
3. Subject has used nicotine-containing products (e.g., cigarettes, 
cigars, chewing tobacco, snuff, electronic cigarettes) within 
6 weeks of Screening. Subjects must refrain from using these 
throughout the study. 
4. Subject has consumed alcohol, xanthine containing products (e.g., 
tea, coffee, cola), caffeine, grapefruit, or grapefruit juice within 
24 h of check-in. Subjects must refrain from ingesting these 
throughout the study.  
5. Subject has a history or evidence of a clinically significant disorder, 
condition, or disease (e.g., cancer, human immunodeficiency virus 
[HIV], hepatic or renal impairment) that, in the opinion of the 
investigator would pose a risk to subject safety or interfere with the 
study evaluation, procedures, or completion. This includes subjects 
with any underlying medical conditions that put subjects at 
increased risk of severe illness from COVID-19 based on the 
Centers for Disease Control and Prevention (CDC) guidelines. 
6. Subject has any signs or symptoms at screening or check-in of any 
study period that are consistent with COVID-19. Per current CDC 
recommendations this includes subjects with the symptoms cough 
or shortness of breath or difficulty breathing, or at least two of the 
following symptoms: fever, chills, repeated shaking with chills, 
muscle pain, headache, sore throat, or new loss of taste/smell. In 
addition, the subject has any other findings suggestive of COVID-
19 risk in the opinion of the investigator. 
7. Subject has known or suspected allergies or sensitivities to any 
study drugs. 
8. Subject has clinical laboratory test results (hematology, serum 
chemistry and urinalysis) at Screening or period check-In that are 
outside the reference ranges provided by the clinical laboratory and 
considered clinically significant by the investigator. Clinical 
laboratory results may be repeated once, as needed, for confirming 
results at Screening and period check-in.   
9. Subject has a positive test result at Screening for HIV 1 or 2 
antibody, hepatitis C virus antibodies, or hepatitis B surface 
antigen. 


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10. Subject is unable or unwilling to undergo multiple venipunctures 
for blood sample collection because of poor tolerability or poor 
venous access. 
11. Female subject is currently pregnant or lactating or was within 3 
months of study enrollment. 
12. Subject has a history of opioid or psychotropic drugs within 60 days 
of the start of the study. 
13. Subject has a history of asthma that has required medication within 
the last five years. 
14. Subject has non-reactive or mishappen pupil(s) or damaged orbit 
structure or surrounding soft tissue is edematous or has an open 
lesion. 
15. Subject has a Mallampati score of >2. 
16. Subject’s Duffin rebreathing data is of poor quality or subject does 
not agree to remain clean-shaven for all days when the Duffin 
rebreathing procedure is performed. 
17. Subject has a history of sleep disorders, Panic disorders, Panic 
Attacks, Generalized Anxiety Disorder, or any associated DSM 
diagnosis or condition. 
18. Subject has a history of or currently has hypoventilation syndrome 
or sleep apnea and is on non-invasive ventilation. 
19. Subject has a history of unexplained syncope, structural heart 
disease, long QT syndrome, heart failure, myocardial infarction, 
angina, unexplained cardiac arrhythmia, TdP, ventricular 
tachycardia, or placement of a pacemaker or implantable 
defibrillator. Subjects will be also excluded if there is a family 
history of long QT syndrome (genetically proven or suggested by 
sudden death of a close relative to cardiac causes at a young age) or 
Brugada syndrome. 
20. Subject has a history of suicidal ideation or previous suicide 
attempts. 
21. Subject has a safety 12-lead ECG result at screening or check-in at 
any study period with evidence of any of the following 
abnormalities:  
x QTc using Fridericia correction (QTcF)>430 msec 
x  PR interval>220 msec or <120msec 
x QRS duration>110 msec 
x Second- or third-degree atrioventricular block 
x Complete left or right bundle branch block or incomplete right 
bundle branch block 
x Heart rate <50 or >90 beats per minute 
x Pathological Q-waves (defined as Q-wave>40 msec) 
x Ventricular pre-excitation  


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22. Subject has a skin condition likely to compromise ECG electrode 
placement. 
23. Any individual with breast implants.  
 
Sample Collection 
The following samples should be collected and processed as follows. 
Number of samples collected throughout the study can be found in the 
Schedule of Events (see Appendix): 
The PK blood samples (6 mL each) will be collected into tubes 
containing K2EDTA, inverted several times to mix the blood with the 
anticoagulant, and placed in an ice bath. Within 30 minutes of 
collection, the samples will be centrifuged for 10 minutes, at 3000 
relative centrifugal force (RCF), at 4°C, by a study team member. 
The plasma will be separated using a disposable plastic pipette and 
equally aliquoted into duplicate cryotube vials labeled as Aliquot A 
(primary) and Aliquot B (backup). The plasma samples will be 
appropriately labeled and stored frozen at -70°C or below within 30 
minutes after aliquoting until shipment. Temperature monitoring logs 
should be maintained and accessible for review by the study monitor.  
The Aliquot A samples (primary) will be shipped first, on dry ice, to the 
bioanalytical laboratory at FDA for processing when requested by the 
sponsor. The Aliquot B samples (backup) will be held for a second 
shipment after completion of all Aliquot A sample shipment(s) and the 
timing of the Aliquot B shipment will be communicated by the sponsor. 
None of the PK blood samples will be stored at the clinical facility for 
future use. 
Pharmacokinetic 
Assessments: 
Pharmacokinetic blood samples will be collected on the following days 
at the approximate times for each study period: 
x Day 5, 6, 11, 12, 20, and 21: 0 (pre-dose), 3, 4, 5, 8 hr (and 24 hr 
for Day 6, 12, and 21) 
x Day 2 and 16: 0 (pre-dose), 2, 3, 4, 5, 6, 8, 12, 24 hr 
Blood samples will be collected by direct venipuncture or by inserting 
an IV catheter. There will be a total of 51 PK samples per participant for 
each study period. 
For each participant, the following PK parameters will be determined 
for oxycodone and oxymorphone (days 6, 12, and 21) and paroxetine 
escitalopram, and escitalopram metabolites (days 2, 5, 6, 11, 12, 16, 20, 
and 21): 
x Maximum observed plasma concentration (Cmax) 
x Area under the plasma concentration time curve (AUC) 


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x Time at which Cmax occurs (Tmax) 
x Elimination rate constant (Kel) 
x Terminal half-life (t1/2) 
x Accumulation ratio (for escitalopram and paroxetine) 
 
Pharmacodynamic 
Assessments:  
 
Rebreathing assessments following Duffin’s rebreathing procedure (see 
separate Standard Operating Procedure [SOP]) will be performed on the 
following study days and time of each study period: 
x Day -1: one hyperoxic and one hypoxic assessment 
x Day 5, 6, 11, 12, 20, and 21: hyperoxic assessments at 0 (pre-
dose), 4 and 5 hours; one hypoxic assessment at 5 hours 
(following the hyperoxic assessment) 
During Duffin’s rebreathing procedure, subjects will be placed in an 
upright position (90o angle) on a bed and connected to the respiration 
measurement set up. Subjects will wear a facemask and breathe from a 
pre-filled rebreathing bag containing approximately 4 L of either a 
hyperoxic-hypercapnic (24% O2, 6% CO2, N2 balanced) or hypoxic-
hypercapnic (6% O2, 6% CO2, N2 balanced) gas mixture. During this 
study, subjects will be asked to breath room air for 5 minutes (relaxation 
stage) and then to hyperventilate (primarily through deep breathing) 
room air voluntarily for 5 minutes (hyperventilation stage). Thereafter, 
subjects will be switched to the rebreathing bag and perform rebreathing 
assessments at one of the 2 different isoxic end tidal PO2, i.e., 150 
mmHg and 50 mmHg. The isoxia at 150 mmHg or 50 mmHg end-tidal 
PO2 will be maintained by providing a computer-controlled flow of 
100% O2 to the rebreathing bag.  
Pupillary assessments (see separate SOP) will be performed before and 
after each rebreathing procedure (except not in between the hyperoxic 
and hypoxic paired assessment) while the ambient light is kept at a 
consistent level. The rubber cup of the pupillometer will be placed on 
the right eye and repeated on the same eye approximately 1 minute later. 
ECG assessments will be performed on the following study days and 
time of each study period: 
x Day 1: 0 (pre-dose) hr 
x Day 2 and 16: 0 (pre-dose), 2, 3, 4, 5, 6, 8, 12, 24 hr 
Ten second 12-lead ECG tracings with the most stable heart rate and 
highest signal-to-noise ratio will be extracted in at least 3 replicates at 
ECG extraction time points during each treatment period. 
During all ECG extraction periods, subjects will be placed in a supine 
position. Three ECG extractions will be performed for a baseline 


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measurement before the first oral dose on day 1 of each treatment 
period. The other ECG extractions/period time matched to the PK 
samples will be obtained before the PK sample collection time. Subjects 
will be isolated (not able to see each other) in a quiet environment that is 
free from external stimuli. 
Different ventilation, cardiovascular, pupillary, sedation, and ECG 
measures that will be summarized include, but are not limited to, the 
following: 
Ventilation and Cardiovascular Assessments:  
x During rebreathing stage 
o VE55 (minute ventilation at the 55mm Hg end tidal CO2 
point) 
o Baseline minute ventilation when end tidal PCO2 is less 
than the ventilatory recruitment threshold (represents 
non-chemoreflex drives to breathe) 
o Ventilatory recruitment threshold (end tidal PCO2 above 
which minute ventilation starts to increase linearly with 
further increases in end tidal PCO2) 
o Slope of the minute ventilation / end-tidal partial 
pressure of carbon dioxide (end-tidal PCO2) regression 
line that reflects the increase in minute ventilation 
relative to the increase in end tidal PCO2 (represents 
chemoreflex sensitivity) 
o Extrapolated ventilation recruitment threshold 
(intersection with X axis) 
x During relaxation stage 
o Minute ventilation, tidal volume, respiratory rate, end-
tidal PCO2, end-tidal PO2, oxygen saturation, and heart 
rate during the relaxation stage 
o Number of apneic events lasting > 10 s during the 
relaxation stage 
 
Pupillary Assessments  
x Maximum pupil diameter before constriction  
x Minimum diameter at peak constriction  
x Percent change between min/max diameter  
x Latency of constriction   
x Average constriction velocity  
x Maximum constriction velocity  
x Dilation velocity after peak constriction  
x Time to reach 75% recovery of maximum diameter  
 


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Sedation scores   
x Ramsey Sedation Scale   
x Visual Analogue Scale   
 
ECG Assessments  
x Change from baseline in QTc, PR, QRS, JTpeakC, TpeakTend and 
heart rate. 
 
In addition, PK/PD relationships will be evaluated between study drugs 
and a subset of pharmacodynamic endpoints (ventilation, pupillary, 
ECG).  
Safety Assessments: 
 
Safety will be evaluated in terms of adverse events (AEs), clinical 
laboratory results (hematology, serum chemistry, and urinalysis), vital 
sign measurements (blood pressure, heart rate, respiratory rate, and oral 
body temperature), safety 12-lead ECG, and physical examination 
findings. 
Sample Size and 
Threshold 
Determination: 
Approximately 25 healthy participants are planned for enrollment. A 
previous study (20 participants) with paroxetine showed a decrease of 
10.2 L/min in VE55 for paroxetine (40 mg) combined with oxycodone 
(10 mg) compared to oxycodone alone after 5 days of dosing with 
paroxetine. Similarly, there was a 9.3 L/min decrease in VE55 for 
paroxetine compared to placebo after 4 days of dosing with paroxetine. 
The standard deviation in assessments was approximately 6.5 L/min. 
Assuming a similar effect size with paroxetine and escitalopram at day 
20 and 21, the planned number of participants allows for a 40% drop out 
rate while maintaining at least 90% power for separate one-sided tests at 
a 0.025 significance level with the multiple primary endpoints.  
Statistical Methods: 
All data will be presented in data listings. Data from subjects excluded 
from an analysis population will be presented in the data listings but not 
included in the calculation of summary statistics. The number of 
subjects who enroll in the study and the number and percentage of 
subjects who complete each assessment will be presented. The 
frequency and percentage of subjects who withdraw or discontinue from 
the study and the reason for withdrawal or discontinuation will be 
summarized. Demographic and baseline characteristics will be 
summarized overall and by treatment for all subjects. 
Descriptive statistics will be used to summarize demographic and 
baseline subject characteristics. For continuous variables, the mean, 
median, standard deviation (SD), minimum, and maximum values will 


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be reported. For categorical (nominal) variables, the number and 
percentage of subjects (or observations) will be reported. 
The rebreathing analysis population will include all subjects who 
completed at least one rebreathing assessment on any day or at any 
timepoint. Specific information on analysis populations for different 
pharmacodynamic measures will be described in the Statistical Analysis 
Plan (SAP). 
 
Primary and Secondary Ventilation Analyses 
Multiple primary analyses are planned for each drug. The first primary 
analysis will be VE55 on day 21 at 5 h (hyperoxic) between oxycodone 
with paroxetine or escitalopram compared to oxycodone alone. The 
second primary analysis will be VE55 on day 20 at 5 h (hyperoxic) 
between paroxetine or escitalopram compared to placebo. Since Day 20 
and 21 are considered multiple primary endpoints, comparisons will 
have an adjustment for multiplicity using a Bonferroni correction (each 
day will be tested at a 0.025 significance level). No adjustments will be 
made for separate testing of paroxetine or escitalopram since the 
treatments are considered separate interventions in the study.  
A linear mixed effects model will be developed using all study data 
from hyperoxic assessments. Fixed effects will include treatment, 
period, sequence, and baseline VE55 (i.e., VE55 obtained at 0 h on Day 
-1 of each treatment period).  Subject will be included as a random 
effect on the intercept.  If a subject’s baseline VE55 for a treatment 
period is not available, then the baseline value for that period will be 
calculated based on the median of all other baseline values for that 
subject from other study periods. If a subject does not have any 
completed baseline VE55 data, the subject will be assigned a baseline 
VE55 equal to the median of the population.  
To demonstrate an effect when oxycodone is combined with paroxetine 
(or escitalopram) compared to oxycodone the upper bound of the one-
sided 97.5% CI of the least-square mean VE55 difference between 
treatments must not overlap 0 L/min.  Similarly, to demonstrate an 
effect of paroxetine (or escitalopram) compared to placebo the upper 
bound of the one-sided 97.5% CI of the least-square mean VE55 
difference between treatments must not overlap 0 L/min. Each 
comparison will be performed separately (i.e.,‘trt’ as ‘paroxetine’ or 
‘escitalopram’).:  
x H0: VE55oxy+trt - VE55oxy  0 L/min 
x HA: VE55oxy+trt - VE55oxy < 0 L/min 


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For secondary endpoints, effects of paroxetine or escitalopram with 
oxycodone compared to oxycodone alone will also be performed using 
the same comparisons on day 6 and day 12. 
As additional secondary endpoints, effects of paroxetine or escitalopram 
alone compared to placebo will be determined on day 5 and 11 using the 
same model. Additional details on testing of ventilation secondary 
endpoints are discussed in the SAP. 
Pharmacokinetics: Concentrations will be determined at approximately 
specified timepoints. Oxycodone and oxymorphone Cmax and AUC will 
be summarized on days 6, 12, and 21 using descriptive statistics. 
Differences in oxycodone or oxymorphone alone compared to exposures 
when coadministered with paroxetine or escitalopram will be compared. 
Cmax and AUC will be log-transformed and the values between study 
arms will be compared using a linear mixed effects model with 
treatment as a categorical variable and participant as a random effect.  
Paroxetine and escitalopram Cmax and AUC will be summarized on days 
2, 5, 6, 11, 12, 16, 20 and 21 using descriptive statistics.  
The PK parameters will be analyzed using noncompartmental methods 
based on actual sampling times. All parameters will be calculated using 
SAS or R software. Mean and individual concentration time profiles 
will be presented in graphs. 
Additional PK parameter analyses including but not limited to measures 
listed under Pharmacokinetic Assessments will be included in the SAP. 
Additional Pharmacodynamics on Ventilatory Assessment Days: 
Mean and standard deviations for baseline minute ventilation, 
ventilatory recruitment threshold, slope of the PCO2-ventilatory 
response curve, and the extrapolated ventilatory recruitment threshold 
will be calculated for each subject at each rebreathing assessment using 
data from the rebreathing stage. Mean and standard deviation for minute 
ventilation, tidal volume, respiratory rate, end-tidal PCO2, end-tidal 
PO2, oxygen saturation, and heart rate will be calculated using data from 
the relaxation stage. Number of apneic events lasting > 10s will be 
counted for each subject, day, and rebreathing assessment during the 
relaxation stage. Full details will be described in a separate SAP. 
Additional pupillary assessments (e.g., ventilation, respiratory rate, heart 
rate, maximum pupil diameter before constriction) as specified in the 
protocol will be reported with standard descriptive statistics. 
ECG Assessments  


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Intensive ECG assessments will be performed on Days 2 and Day 16. 
The QT interval will be corrected for heart rate using Fridericia’s 
formula (QTc=QT/RR1/3). The J-Tpeak interval will be corrected for heart 
rate using the formula (J-TpeakC = J-Tpeak/RR0.58). Baseline will be the 
mean of the 3 predose ECG extractions of Day 1. 
Exposure-response analyses will be performed for the change from 
baseline in QTc (and other ECG measurements; see ECG Analysis 
Plan), where the mean of the 3 predose ECG readings on Day 1 will be 
used as the Baseline. The concentration of the drug will be used as a 
covariate. Exposure-response analysis will be done following most 
recent best practices in concentration-QTc modeling. Additional details 
will be specified in the ECG Analysis Plan. 
 
Safety 
The safety population will include all subjects who receive at least 1 
dose of the study drug. All AEs will be coded using the Medical 
Dictionary for Regulatory Activities (MedDRA). The incidence of AEs, 
organized by system organ class and preferred term, will be summarized 
with a focus on treatment-emergent AEs. Vital sign measurements will 
be summarized using descriptive statistics by time point. All values will 
be evaluated for clinically notable results. Data for additional safety 
parameters (e.g., physical examination findings) will be listed. 
Date of Protocol: 
21 July 2022 
 
 
 


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1. INTRODUCTION 
A well-known and potentially fatal adverse reaction associated with opioid 
administration, particularly in the scenario of misuse, abuse, or when co-administered 
with certain other drugs is that people ‘stop breathing’. Research suggests this is caused 
by a reduced respiratory response to counteract increasing levels of systemic carbon 
dioxide (CO2). In August 2016, the U.S. Food and Drug Administration (FDA) included 
boxed warnings about increased potential for respiratory depression with co-use of 
benzodiazepines and opioids.1  In response to this action, concerns were raised because 
patients may be prescribed other psychotropic drugs that may have similar adverse 
reactions when combined with opioids.  
Subsequently, FDA performed a review of the literature and identified 13 psychotropic 
drugs for evaluation in an in vivo animal study (using a rat model). The in vivo study 
identified 4 drugs that had significant effects when combined with oxycodone on arterial 
carbon dioxide.2 Two drugs (quetiapine and paroxetine) were selected for further 
evaluation in a human clinical study evaluating drug effects on hypercapnic ventilation.  
To study the effects of opioids alone or in combination with other psychotropic drugs on 
ventilation, FDA used a procedure referred to as Read rebreathing.3-4 With Read 
rebreathing, study participants rebreathe through a circuit with increased level of O2 and 
CO2 (93% O2 and 7% CO2). The artificially increased levels of CO2 trigger the subjects to 
increase ventilation. This “hypercapnic ventilatory response” can be decreased by 
opioids, benzodiazepines, and other drugs.5-19     
The previous study, which included 5-days of study drug dosing with oxycodone 
administered on day 1 or 5 showed quetiapine co-administered with oxycodone did not 
cause a significant decrease in hypercapnic ventilation compared to oxycodone alone.20  
In contrast, paroxetine caused a decrease in hypercapnic ventilation compared to 
oxycodone alone, and an additive effect was seen when combined with oxycodone. This 
mechanism is due to a direct pharmacodynamic effect, rather than a pharmacokinetic 
interaction and most likely due to its serotonergic properties. Paroxetine is highly 
selective for inhibiting the serotonin transporter versus other monoamine transporters and 
other receptors in general.21-22 Although different types of serotonergic receptors and 
neurons can have differential effects on breathing, paroxetine does not bind to serotonin 
receptors at clinically-relevant exposures.23-24 In addition, nonclinical and clinical studies 
have shown different selective serotonin reuptake inhibitors (SSRIs) can have 
independent effects on ventilation, though SSRIs have not been shown to cause severe 
respiratory depression on their own.25-43 This supports the need for additional 
investigation on the effects of serotonergic drugs. Escitalopram is highly selective for the 
serotonin transporter, has low selectivity for serotonin receptors and muscarinic 


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receptors, and is widely prescribed, making it a good candidate as a second SSRI to 
evaluate in this study. 
The previous study evaluated effects on ventilation over 5-days of dosing. SSRIs take 
approximately 3 weeks to reach maximal therapeutic effect, which correlates with the 
time required for pre-synaptic inhibitory serotonergic receptors to desensitize.44-46 SSRI 
effects on ventilation in the proposed study would be evaluated for a similar period of 
time to confirm if effects on ventilation persist under steady state conditions.   
Finally, an additional modification in the proposed study will be the assessment of 
hypercapnic ventilation under hyperoxic and hypoxic gas levels using a modified Read 
rebreathing approach referred to as Duffin rebreathing. One limitation of the rebreathing 
procedure from the previous study design is all measurements are performed under 
hyperoxic conditions, which can have independent effects on ventilation. In addition, the 
data cannot necessarily be used to extrapolate to the dynamic changes in PO2 and PCO2 
that occur during real-world drug-induced respiratory depression when a patient is 
breathing room air. Duffin modified the Read rebreathing method to include 1) 
hyperventilation (primarily through deep breathing) prior to rebreathing to achieve an end 
tidal PCO2 or approximately 20-25 mm Hg prior to rebreathing, 2) maintaining an isoxic 
end tidal PO2 during rebreathing, and 3) repeating rebreathing at 2 different isoxic end 
tidal PO2 levels (i.e., at 150 mm Hg and 50 mm Hg). These modifications, which have 
been used by investigators for decades, allow for critical physiological measurements and 
thresholds to be captured that can then be used to model the effects of drugs when there 
are dynamic changes in PO2 and PCO2, such as during a real-world opioid overdose.47-52 
 
2. STUDY OBJECTIVES 
2.1 Primary Objectives 
x To study ventilatory effects of SSRIs (paroxetine or escitalopram) combined with 
oxycodone compared to oxycodone alone after 21 days of SSRI dosing. 
x To study ventilatory effects of SSRIs (paroxetine or escitalopram) compared to 
placebo after 20 days of SSRI dosing.   
2.2 Secondary Objectives  
x To compare ventilatory effects of SSRIs (paroxetine or escitalopram) combined 
with oxycodone compared to oxycodone alone after 6 and 12 days of SSRI 
dosing. 


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x To compare ventilatory effects of SSRIs (paroxetine or escitalopram) compared to 
placebo after 5 and 11 days of SSRI dosing. 
2.3 Exploratory Objectives  
x To study whether paroxetine or escitalopram affects the pharmacokinetics of 
oxycodone. 
x To evaluate differences in hypercapnic ventilatory response under hyperoxic or 
hypoxic rebreathing. 
x To study whether there is a direct pharmacodynamic interaction between 
paroxetine or escitalopram and oxycodone. 
x To summarize additional pharmacokinetic parameters and pharmacodynamic 
measurements collected during the study. 
 
3. STUDY ENDPOINTS 
3.1 Primary Endpoints 
The following primary endpoints will be evaluated: 
x Minute ventilation at 55mm Hg end tidal CO2 (VE55) under hyperoxic conditions 
on day 21 
x VE55 under hyperoxic conditions on day 20  
3.2 Secondary Endpoints  
The following secondary endpoints will be evaluated: 
x VE55 under hyperoxic conditions on days 6 and 12 
x VE55 under hyperoxic conditions on days 5 and 11 
3.3 Exploratory Endpoints 
The following exploratory PK parameters will be determined for oxycodone and 
oxymorphone (days 6, 12, and 21) and paroxetine, escitalopram, and escitalopram 
metabolites (days 2, 5, 6, 11, 12, 16, 20, and 21): 
x Maximum observed plasma concentration (Cmax) 
x Area under the plasma concentration time curve (AUC) 
x Time at which Cmax occurs (Tmax) 
x Elimination rate constant (Kel) 


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x Terminal half-life (t1/2) 
x Accumulation ratio (for escitalopram and paroxetine) 
Additionally, the following exploratory PD markers may be evaluated:  
Ventilation and Cardiovascular Assessments:  
x During rebreathing stage 
o VE55 (minute ventilation at the 55mm Hg end tidal CO2 point) 
o Baseline minute ventilation when end tidal PCO2 is less than the 
ventilatory recruitment threshold (represents non-chemoreflex drives to 
breathe) 
o Ventilatory recruitment threshold (end tidal PCO2 above which minute 
ventilation starts to increase linearly with further increases in end tidal 
PCO2) 
o Slope of the minute ventilation / end-tidal partial pressure of carbon 
dioxide (end-tidal PCO2) regression line that reflects the increase in 
minute ventilation relative to the increase in end tidal PCO2 (represents 
chemoreflex sensitivity) 
o Extrapolated ventilation recruitment threshold (intersection with X axis) 
x During relaxation stage 
o Minute ventilation, tidal volume, respiratory rate, end-tidal PCO2, end-
tidal PO2, oxygen saturation, and heart rate during the relaxation stage 
o Number of apneic events lasting > 10 s during the relaxation stage 
Pupillary Assessments  
x Maximum pupil diameter before constriction  
x Minimum diameter at peak constriction  
x Percent change between min/max diameter  
x Latency of constriction   
x Average constriction velocity  
x Maximum constriction velocity  
x Dilation velocity after peak constriction  
x Time to reach 75% recovery of maximum diameter  
Sedation scores   
x Ramsey Sedation Scale   


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x Visual Analogue Scale   
ECG Assessments  
x Change from baseline in QTc, PR, QRS, J-TpeakC, Tpeak-Tend and heart rate. 
An exploratory endpoint is the pharmacokinetic/pharmacodynamic (PK/PD) relationship 
for study drugs when administered alone versus in combination. 
 
4. INVESTIGATIONAL PLAN 
4.1 Study Design 
This study will be a randomized, double blind, three period crossover study with 
approximately 25 healthy volunteer participants. This study will include three 21-day 
treatment periods with a 3-week washout between each period. Each subject will be 
randomized to 1 of 6 treatment sequences (i.e., ABC, ACB, BAC, BCA, CAB, CBA). 
FDA will prepare the randomization schedule. 
Table 4-1: Study Schedule  
 
 
 
Table 4-2: Study Treatments: 
 
Participants will enter the clinic on a staggered basis in cohorts of approximately five so 
that no more than five subjects are undergoing rebreathing on any given day. Subjects 
will be staggered to allow for direct safety overview by medical staff during Duffin’s 
rebreathing.  
Participants will receive either placebo, paroxetine, or escitalopram on days 1-21 for each 
period. Oxycodone will be administered on days 6, 12, and 21 of each period. Dosing of 
the study drugs will occur at time 0 on each day. Oxycodone dosing will occur at 3 h so 
Day -1  
Days 1-21 
Days 22-42 
Days 42-63 
Days 64-84  
Days 85-105 
Day 106 
Check-in  
Period 1 
Washout 
Period 2  
Washout  
Period 3  
Check-out 
Treatment 
Day 
1-5 
6 
7-11 
12 
13-20 
21 
A 
Placebo 
Placebo +  
10 mg oxycodone 
Placebo 
Placebo +  
10 mg oxycodone 
Placebo 
Placebo + 
10 mg oxycodone 
B 
40 mg 
paroxetine  
40 mg paroxetine 
+ 10 mg 
oxycodone 
60 mg paroxetine 60 mg paroxetine 
+ 10 mg 
oxycodone 
60 mg paroxetine 60 mg paroxetine 
+ 10 mg 
oxycodone 
C 
20 mg 
escitalopram 
20 mg 
escitalopram +  
10 mg oxycodone 
30 mg 
escitalopram 
30 mg 
escitalopram +  
10 mg oxycodone 
30 mg 
escitalopram 
30 mg 
escitalopram + 10 
mg oxycodone 


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that maximum concentration occurs for all drugs is at approximately the same time. 
Participants will also receive ondansetron 4 mg 30 min before oxycodone administration.  
Participants will be confined to the study clinic from Day -1 the morning of Day 22 for 
each period. There will be a three-week washout between each period. Subjects will be 
discharged from the study after completion of all study procedures. If a subject 
discontinues from the study prematurely, all procedures scheduled for the end of the 
study will be performed. Meal timing and components, activity levels, and general 
conditions in the study clinic will be as similar as possible on the treatment days. 
Upon return to clinic, on Days 42 & 84, eligibility criteria to continue study participation 
will be reviewed (see Schedule of Events for criteria listed on Days 42 & 84), any 
changes in medical history (including concomitant medications) will be documented. 
4.1.1 Risk/Benefit 
Subjects will be informed that participation in a human clinical pharmacology study like 
the present one cannot be of benefit to healthy volunteers. Nevertheless, the information 
from the physical examination, vital sign measurements, and ECG results may be shared 
with the subject’s personal physician if this is the subject’s choice. Subjects will be 
informed that it is also their choice to inform their personal physician that they are 
participating in this research study. 
Subjects will be informed that their contribution to the study is of major importance to 
agencies like the FDA to understand the potential for respiratory depression with 
coadministration of SSRIs and opioids. However, since this is a study involving healthy 
volunteers, subjects will be informed that they have the option not to participate. 
Subjects will be informed that opioids have a box warning for life-threatening respiratory 
depression. To mitigate potential events, subjects will undergo continuous pulse oximetry 
monitoring, there will be stopping rules for the treatment, rescue medications for 
oxycodone will be present, and a safety management plan for staff will be implemented 
during the study which includes a requirement to have 1:1 advanced cardiac life support 
staff to subjects in addition to the study investigator.   
Subjects will be informed that they may be exposed to risks associated with the 
pharmacological properties of the study drug and the study procedures. The following 
summary of potential AEs for the study drugs will be provided to and discussed with the 
subjects: 
1. Oral oxycodone 5 mg IR tablets (up to 10 mg): The most common adverse events 
include typical opioid-related adverse reactions: nausea, constipation, vomiting, 
headache, pruritus, insomnia, dizziness, asthenia, agitation, anxiety, hallucinations, 
nightmares, and somnolence. Serious adverse reactions include: respiratory 


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depression, respiratory arrest, circulatory depression, cardiac arrest, hypotension, 
and/or shock.53 
2. Oral paroxetine 20 mg IR tablets (up to 60 mg): The most common adverse events 
include: somnolence, insomnia, agitation, tremor, anxiety, dizziness, constipation, 
nausea, diarrhea, dry mouth, vomiting, flatulence, asthenia, erectile dysfunction, 
delayed ejaculation, vaginal paresthesia, itching, and discharge, yawning, infection, 
sweating, decreased appetite, nervousness, impotence, and libido decreased.54 
3. Oral escitalopram 10 mg tablets (up to 30 mg): The most common adverse events 
include: insomnia, ejaculation disorder, drowsiness, impotence, nausea, sweating 
increased, fatigue, somnolence, decreased libido, anorgasmia, headache, diarrhea, dry 
mouth, dizziness, constipation, and indigestion. Additional adverse events include 
hypersensitivity reactions, seizures, syncope, QT interval prolongation, cardiac 
arrhythmias, enhanced clotting, and hepatic enzyme elevation.55  
4. Oral ondansetron 4 mg tablets given prior to oxycodone for nausea/vomiting and 4 
mg IV as needed: The most common adverse events include: diarrhea, headache, 
fever, malaise, fatigue, constipation, and hypoxia. Additional adverse events include: 
hypersensitivity reactions, including anaphylaxis and bronchospasm, QT interval 
prolongation and Torsade de Pointes, and serotonin syndrome (usually when 
prescribed with another serotoninergic medication such as select serotonin reuptake 
inhibitors and serotonin-norepinephrine reuptake inhibitors).56 
Selected doses of individual drugs are within the FDA approved labeled doses or are 
doses that have been used in prior healthy participant studies for similar durations. As 
drug combinations are being studied, the doses of oxycodone are less than that which has 
been used in prior studies in opioid naïve healthy volunteers undergoing rebreathing5-6,11 
or other similar procedures (see below). 
x Oxycodone - A prior study of the effects of decreased ventilatory response to 
hypercapnia of oxycodone with and without ethanol in opioid naïve healthy 
volunteers (young and elderly participants) used a dose of oxycodone 20 mg.5-6 
An additional ongoing study from these authors (unpublished) is using a dose of 
oxycodone 40 mg in opioid naïve healthy volunteers. Our previous study 
(unpublished) used 10 mg oxycodone, which decreased ventilation approximately 
5 L/min from baseline and was well-tolerated by study participants with no 
discontinuations due to the selected dose. The present study will also use 
oxycodone 10 mg.  
x Paroxetine – Paroxetine will be administered 40 mg/day for 6 days and 60 mg/day 
for 15 days. This is within the maximum labeled dose of paroxetine (60 mg/day). 
The dose is higher than the typical starting dose of 20 mg/day that is titrated up 


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over 1-week intervals, however starting doses up to 60 mg have been given safely 
to healthy volunteers.51 
x Escitalopram – Escitalopram will be administered at 20 mg/day for 6 days and 30 
mg/day for 15 days. This is above the maximal labeled dose of escitalopram (20 
mg/day) but doses up to 30 mg/day have been evaluated in a thorough QT study. 
The exposure with 30 mg is similar to the steady state concentration expected in 
CYP2C19 poor metabolizers following a therapeutic dose of 20 mg.55 
x Ondansetron – Ondansetron will be administered as a single 4 mg oral dose in all 
treatment periods prior to administration of oxycodone and will be available as 4 
mg IV as needed for nausea and vomiting. A dose of 4 mg is less than the highest 
labeled dosing for other ondansetron indications (24 mg as a single dose or 8 mg 
twice a day).56  
The study drugs will not be administered to anyone who is pregnant. All women must 
take a pregnancy test before receiving any study drug in this study. All women of 
childbearing potential enrolled on this study will be informed that they must use effective 
birth control methods (abstinence, intrauterine device, and contraceptive foam and a 
condom [i.e., double-barrier method]) during treatment. Subjects will be informed that 
they must notify the investigator if they or their female partners become pregnant during 
the course of the study. If a subject becomes pregnant, she will be informed that neither 
Spaulding Clinical Research nor the sponsor will be responsible for the cost of any 
obstetric or related care, or for the child’s care. 
Subjects will be informed that insertion of an IV catheter may be required for blood 
sample collection and, during insertion of the catheter, soreness, bruising, or infection at 
the insertion site are possible but unlikely. Subjects will also be informed that dizziness 
and lightheadedness may occur during direct venipuncture, insertion of the IV catheter, or 
during blood collection. 
Subjects will be informed that they will be participating in the Duffin rebreathing 
SURFHGXUHZKHUHWKH\ZLOOEUHDWKHௗDK\SHUR[LF-hypercapnic (24% O2, 6% CO2, N2 
balanced) or hypoxic-hypercapnic (6% O2, 6% CO2, N2 balanced) gas mixture through a 
mask. They will be informed that this mixture of oxygen, carbon dioxide and nitrogen 
provided will be different than is normally found in room air (21% O2, 0.04% CO2, N2 
balanced with minor amounts of other gasses). Subjects will be informed that the 
different gas concentrations, in particular the higher level of carbon dioxide breathed in, 
may result in a feeling of needing to breathe faster or more deeply. Subjects will be 
informed that this procedure has been used in many previous physiologic measurement 
studies and is non-LQYDVLYH'XULQJVFUHHQLQJVXEMHFWVZLOOEHVKRZQௗWKHUHEUHDWKLQJ
equipment and will be trained how to use it to understand if the procedure is tolerable.  


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Subjects will be informed that the confidentiality of their data will be respected at all 
times according to state law, and the study personnel handling their study data are bound 
by confidentiality agreements. 
Subjects will be informed that extra precautions will be put in place, including required 
screening tests, that will limit the risk of COVID-19. Precautions will be documented in a 
COVID-19 risk management plan. Subjects will be informed that despite the extra 
precautions there is still a risk of them contracting COVID-19. Any changes to the 
COVID-19 precautions (e.g., due to updated CDC recommendations or new testing 
becoming available) will be documented in the COVID-19 risk mitigation plan.  
Subjects will be informed that the study drug and all tests, procedures, and visits required 
by the study are provided at no cost to them. If subjects become ill or physically injured 
because of participation in this study, they will be informed that costs of treatment will 
not be covered by the sponsor. 
4.2 Selection of Study Population 
Subjects will be screened, and the data collected will be reviewed by the principal 
investigator. Only those subjects who meet all the eligibility criteria will be enrolled. 
Approximately 25 healthy subjects are planned for enrollment. Every effort will be made 
to maintain an approximate 50:50 male-to-female sex distribution. 
4.2.1 Inclusion Criteria 
Subjects who meet all the following inclusion criteria will be eligible to participate in the 
study:  
1. Subject signs an IRB-approved written informed consent and privacy language as 
per national regulations (e.g., Health Insurance Portability and Accountability Act 
authorization) before any study-related procedures are performed.  
2. Subject is a healthy, non-smoking man or woman, 18 to 50 years of age, inclusive, 
who has a body mass index of 18.5 to 33.0 kg/m2, inclusive, at Screening. 
3. Subject has normal medical history findings, clinical laboratory results, vital sign 
measurements, pulse oximetry, 12-lead ECG results, and physical examination 
findings at screening or, if abnormal, the abnormality is not considered clinically 
significant (as determined and documented by the investigator or designee). 
4. Subject must have a negative test result for alcohol and drugs of abuse at screening 
and check-in days.  
5. Subject must test negative for severe acute respiratory syndrome corona virus 2 
(SARS-CoV-2) by a rapid antigen test at check-in for all study periods. If a 
subject’s test comes back as invalid, the test can be repeated. 


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6. Female subjects must be of non-childbearing potential (confirmed with follicle-
stimulating hormone levels > 40 mIU/mL) or, if they are of childbearing potential, 
they must: 1) have been strictly abstinent for 1 month before check-in (Day -1) and 
agree to remain strictly abstinent for the duration of the study and for at least 
1month after the last application of study drug; OR 2) be practicing 2 highly 
effective methods of birth control (as determined by the investigator or designee; 
one of the methods must be a barrier technique) from at least 1 month before check-
in (Day -1) until at least 1 month after the end of the study.  
7. Male subjects must agree to practice 2 highly effective methods of birth control (as 
determined by the investigator or designee) from at least 1 month before check-in 
(Day -1) until at least 1 month after the last dose of study drug. 
8. Subject is highly likely (as determined by the investigator) to comply with the 
protocol defined procedures and to complete the study. 
4.2.2 Exclusion Criteria 
Subjects who meet any of the following exclusion criteria will not be eligible to 
participate in the study: 
1. Subject has used any prescription or nonprescription drugs (including aspirin or 
NSAIDs and excluding oral contraceptives and acetaminophen) within 14 days or 5 
half-lives (whichever is longer) or complementary and alternative medicines within 
28 days before the first dose of study drug. This includes prescription or 
nonprescription ophthalmic drugs. 
2. Subject is currently participating in another clinical study of an investigational drug 
or has been treated with any investigational drug within 30 days or 5 half-lives 
(whichever is longer) of the compound. 
3. Subject has used nicotine-containing products (e.g., cigarettes, cigars, chewing 
tobacco, snuff, electronic cigarettes) within 6 weeks of Screening. Subjects must 
refrain from using these throughout the study. 
4. Subject has consumed alcohol, xanthine containing products (e.g., tea, coffee, cola), 
caffeine, grapefruit, or grapefruit juice within 24 h of check-in. Subjects must refrain 
from ingesting these throughout the study.  
5. Subject has a history or evidence of a clinically significant disorder, condition, or 
disease (e.g., cancer, human immunodeficiency virus [HIV], hepatic or renal 
impairment) that, in the opinion of the investigator would pose a risk to subject 
safety or interfere with the study evaluation, procedures, or completion. This 
includes subjects with any underlying medical conditions that put subjects at 


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increased risk of severe illness from COVID-19 based on the Centers for Disease 
Control and Prevention (CDC) guidelines. 
6. Subject has any signs or symptoms at screening or check-in of any study periods that 
are consistent with COVID-19. Per current CDC recommendations this includes 
subjects with the symptoms cough or shortness of breath or difficulty breathing, or at 
least two of the following symptoms: fever, chills, repeated shaking with chills, 
muscle pain, headache, sore throat or new loss of taste/smell. In addition, the subject 
has any other findings suggestive of COVID-19 risk in the opinion of the 
investigator. 
7. Subject has known or suspected allergies or sensitivities to any study drugs. 
8. Subject has clinical laboratory test results (hematology, serum chemistry and 
urinalysis) at Screening or period check-in that are outside the reference ranges 
provided by the clinical laboratory and considered clinically significant by the 
investigator. Clinical laboratory results may be repeated once, as needed, for 
confirming results at Screening and period check-in.   
9. Subject has a positive test result at Screening for HIV 1 or 2 antibody, hepatitis C 
virus antibodies, or hepatitis B surface antigen. 
10. Subject is unable or unwilling to undergo multiple venipunctures for blood sample 
collection because of poor tolerability or poor venous access. 
11. Female subject is currently pregnant or lactating or was within 3 months of 
enrollment. 
12. Subject has a history of opioid or psychotropic drugs within 60 days of the start of 
the study. 
13. Subject has a history of asthma that has required medication within the last five 
years. 
14. Subject has non-reactive or mishappen pupil(s) or damaged orbit structure or 
surrounding soft tissue is edematous or has an open lesion. 
15. Subject has a Mallampati score of >2. 
16. Subject’s Duffin rebreathing data is of poor quality or subject does not agree to 
remain clean-shaven for all days when the Duffin rebreathing procedure is 
performed. 
17. Subject has a history of sleep disorders, Panic disorders, Panic Attacks, Generalized 
Anxiety Disorder, or any associated DSM diagnosis or condition. 


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18. Subject has a history of or currently has hypoventilation syndrome or sleep apnea 
and is on non-invasive ventilation. 
19. Subject has a history of unexplained syncope, structural heart disease, long QT 
syndrome, heart failure, myocardial infarction, angina, unexplained cardiac 
arrhythmia, TdP, ventricular tachycardia, or placement of a pacemaker or 
implantable defibrillator. Subjects will be also excluded if there is a family history of 
long QT syndrome (genetically proven or suggested by sudden death of a close 
relative to cardiac causes at a young age) or Brugada syndrome. 
20. Subject has a history of suicidal ideation or previous suicide attempts. 
 
21. Subject has a safety 12-lead ECG result at Screening or check-in at any study period 
with evidence of any of the following abnormalities:  
x QTc using Fridericia correction (QTcF)>430 msec 
x  PR interval>220 msec or <120msec 
x QRS duration>110 msec 
x Second- or third-degree atrioventricular block 
x Complete left or right bundle branch block or incomplete right bundle branch 
block 
x Heart rate <50 or >90 beats per minute 
x Pathological Q-waves (defined as Q-wave>40 msec) 
x Ventricular pre-excitation  
22. Subject has a skin condition likely to compromise ECG electrode placement. 
23. Any individual with breast implants.  
4.3 Screening Failures 
Subjects who sign and date the informed consent form but who fail to meet the inclusion 
and exclusion criteria are defined as screening failures. A screening log, which 
documents the subject initials and reason(s) for screening failure, will be maintained by 
the investigator for all screening failures. A copy of the log should be retained in the 
investigator’s study files. 
If a subject fails the screening process because of an abnormal laboratory result, they can 
receive a copy of the results upon request. The investigator will determine if follow-up 
for the abnormal laboratory result is needed and will encourage the subject to follow-up 
with his or her personal physician as appropriate. All subjects will be informed as to the 


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reason(s) they are excluded from study participation, even if follow-up is not required. If 
a subject fails the screening process because of a positive test result for human 
immunodeficiency virus or hepatitis, the positive result will be reported to local health 
authorities as required by law. 
4.4 Termination of Study or Investigational Site 
4.4.1 Criteria for Termination of the Study 
The study will be completed as planned unless one of the following criteria is satisfied 
that requires early termination of the study. 
x New information regarding the safety or efficacy of the study drug(s) that indicates a 
change in the known risk profile for the study drug(s), such that the risk is no longer 
acceptable for subjects participating in the study. 
x Significant violation of Good Clinical Practice (GCP) that compromises the ability to 
achieve the primary study objective or compromises subject safety. 
4.4.2 Criteria for Termination of the Investigational Site 
The study site may be terminated if the site (including the investigator) is found in 
significant violation of GCP, the protocol, the contractual agreement, or is unable to 
ensure adequate performance of the study. 
In the event that the sponsor elects to terminate the study or the investigational site, a 
study-specific procedure for early termination will be provided by the sponsor; the 
procedure will be followed by the applicable investigational site during the course of 
termination. 
4.5 Criteria for Subject Withdrawal 
Subjects may withdraw from the study at any time at their own request, or they may be 
withdrawn by the investigator without the approval of the subject based on the 
investigator’s clinical judgment. A subject is not required to provide a written request to 
withdraw from the study; however, a written request is required if a subject withdraws 
consent for his or her personal data to be used for study-related purposes. 
A subject may be discontinued for any of the following reasons: 
x AE: The subject has experienced an AE that, in the opinion of the investigator, 
requires early termination. The appropriate electronic case report form (eCRF) must 
be completed for each AE. If a subject is discontinued from the study due to an AE, 
the investigator is required to follow-up with the subject until the event resolves or 
becomes stable. If a subject dies during the study, the cause of death must be reported 
as a serious AE (SAE), with an outcome of death noted in the eCRF. 


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x Protocol Violation: The subject failed to meet protocol entry criteria or did not adhere 
to protocol requirements, and continued participation poses an unnecessary risk to the 
subject’s health. 
x Withdrawal by Subject: The subject (or other responsible individual [e.g., caregiver]) 
wishes to withdraw from the study in the absence of a medical need. 
NOTE: Withdrawal due to an AE should not be recorded in the “voluntary 
withdrawal” category. 
x Study Terminated by Sponsor: The sponsor, IRB, FDA, or other regulatory agency 
terminates the study. 
x Pregnancy: The subject is found to be pregnant. 
NOTE: If the subject is found to be pregnant, the subject must be withdrawn 
immediately. The pregnancy will be followed-up to term, and the outcome, including 
any premature termination will be recorded. All live births must be followed for a 
minimum of 30 days or until the first well-baby visit. 
x Other. 
NOTE: This category records withdrawals caused by an accidental or a medical 
emergency, unblinding, and other rare cases. The specific reason should be recorded 
in the comment space of the eCRF. 
4.5.1 Handling of Withdrawals 
The investigator may terminate a subject’s study participation at any time during the 
study when the subject meets the criteria described in Section 4.5. In addition, a subject 
may discontinue his or her participation without giving a reason at any time during the 
study. Subjects will be informed that their participation in the study is voluntary, that 
refusal to participate will involve no penalty or loss of benefits to which the subject is 
otherwise entitled, and that the subject may discontinue participation at any time without 
penalty or loss of benefits to which the subject is otherwise entitled. 
Should a subject’s participation be discontinued, the primary reason for termination must 
be recorded. In addition, efforts should be made to perform all procedures scheduled for 
the early termination visit. Any data and samples collected before subject withdrawal will 
become the property of the sponsor. 
4.5.2 Replacement of Subjects 
Approximately 25 healthy subjects are planned for enrollment and will be randomized to 
1 of 6 treatment sequences.  


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4.6 Study Visits 
4.6.1 Recruitment 
Recruitment materials (e.g., internet, radio, and print advertisements, social media posts) 
will be approved by the local IRB before telephone screening. The sponsor is responsible 
for registration of the study on clinicaltrials.gov. Recruitment may not occur until the 
study is fully registered on clinicaltrials.gov. 
4.6.2 Compensation 
Subjects will be offered payment for Screening; however, if the results of their alcohol 
and drug screening tests are positive, they will not be compensated. Subjects who 
complete the entire study will receive payment according to the schedule provided in the 
informed consent form. No special incentives are offered. Final payment will not be 
released until all follow-up procedures have been completed and accepted by the 
investigator. 
If a subject chooses to withdraw from the study prematurely, he or she will only be 
compensated for completed days. If subjects are withdrawn for medical reasons or if the 
study is halted temporarily or permanently, the subjects will receive compensation 
proportional to the time spent in the study. No compensation will be provided if a subject 
is dismissed from the study for noncompliance (e.g., improper conduct, ingesting alcohol 
and/or drugs [including recreational drugs], tampering with the study drug, consuming 
any prohibited foods or beverages). 
If subjects are required to stay in the clinic for a longer period for safety reasons, they 
will be compensated at a rate proportional to the entire compensation for the study. If a 
subject becomes ill or physically injured because of participation in this study, the subject 
will be referred for treatment. 
4.6.3 Screening  
The following procedures and assessments will be performed at Screening (Day -28 to -
2): 
x Obtain informed consent/HIPAA authorization. The informed consent process will be 
performed by a clinical research nurse in a private room. The subject will be given 
unlimited time to ask questions regarding study participation, and each subject will be 
questioned to ensure their understanding. 
After informed consent is obtained: 
x Review inclusion/exclusion criteria to confirm subject eligibility 
x Record demographic information 


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x Measure height, weight, and calculate body mass index 
x Perform serology screening (HIV antigen/antibody [Ag/Ab] Combo 1/2, HepC 
antibody, HBsAg) 
x Record medical history 
x Perform alcohol and drug screening (amphetamines, barbiturates, benzodiazepines, 
cannabinoids, cocaine, alcohol, opiates, phencyclidine, propoxyphene, and 
methadone) 
x Perform urine cotinine test 
x Perform a serum pregnancy test (female subjects only) 
x Perform FSH measuring (postmenopausal [i.e., without menses for two years] female 
subjects only) 
x Record prior medications 
x Monitor for AEs 
x Perform clinical laboratory tests (hematology, serum chemistry, and urinalysis) 
x Measure vital signs (blood pressure, heart rate, respiratory rate, pulse oximetry, and 
oral body temperature) 
x Perform a safety 12-lead ECG 
x Perform a complete physical examination, including assessment of participant’s 
Mallampati score 
x Examine pupils for shape and reactivity 
x Perform Duffin’s rebreathing under hyperoxic and hypoxic conditions 
4.6.4 Study Periods 
This study will be a randomized, double blind, three period crossover study. This study 
will include three 21-day treatment periods with a 3-week washout between each period. 
Participants will be confined to the study clinic from day -1 until the first day of each 
washout period. There will be a three week washout between each period. Subjects will 
be discharged from the study after completion of all study procedures. 
4.6.4.1 Check-In 
The following procedures and assessments will be performed at Check-in [Day -1] and 
when participants check back into the clinic after each washout period: 


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x Perform/review results from SARS-CoV-2 rapid antigen test  
x Review inclusion/exclusion criteria to confirm subject eligibility 
x Review medical history 
x Perform alcohol and drug screening (amphetamines, barbiturates, benzodiazepines, 
cannabinoids, cocaine, alcohol, opiates, phencyclidine, propoxyphene, and 
methadone) 
x Perform urine cotinine test 
x Perform a serum pregnancy test at all check-ins (female subjects only) 
x Admit subject to the study clinic 
x Randomization (after completion of check-in procedures or just before dosing on 
Day 1 of each study period)  
x Record concomitant medications 
x Monitor for AEs 
x Perform clinical laboratory tests (hematology, serum chemistry, and urinalysis) 
x Measure vital signs (blood pressure, heart rate, respiratory rate, pulse oximetry, and 
oral body temperature) 
x Perform a safety 12-lead ECG (only at initial check-in of each study period) 
x Perform a comprehensive physical examination 
x Perform Duffin’s rebreathing procedure under hyperoxic and hypoxic conditions 
x Collect whole blood sample for CYP2D6 genotype/phenotype (only at check-in for 
first study period) 
4.6.4.2 Treatment 
The following procedures and assessments will be performed during the treatment period 
according to the Schedule of Events (Appendix A): 
x Monitor for AEs 
x Record concomitant medications 
x Perform clinical laboratory tests at specified time points 
x Administer study drug according to the randomization schedule following all other 
pre-dose examinations and specimen collection 


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x Measure vital signs (blood pressure, heart rate, respiratory rate, pulse oximetry, and 
oral body temperature). If vital signs are scheduled at the same time as another event, 
vital signs will be measured after the ECG, but before blood sample collection 
x Perform safety 12-lead ECGs at timepoints specified in Section 4.7.2.4. If scheduled 
for the same time, safety 12-lead ECGs will always be performed before vital sign 
measurement and blood sample collection 
x Perform pulse oximetry monitoring as specified in Appendix A – Schedule of Events 
x Perform rebreathing assessments following Duffin’s rebreathing procedure at 
timepoints specified in Section 4.7.2.1. Preparatory steps for the Duffin Rebreathing 
procedure (i.e., relaxation, hyperventilation) should begin prior to the scheduled 
sample time. Timing of sample collection is planned so that the PD assessment begins 
at the specified time and a 3- to 15-minute window is planned for completion of the 
procedure. 
x Perform pupillary assessments as specified in Appendix A – Schedule of Events 
x Perform sedation assessments as described in Section 4.7.2.3 (Ramsey Sedation Scale 
and Visual Analogue Scale) 
x Collect PK blood samples (6 mL) at timepoints specified in Section 4.7.1.1 
4.6.4.3 Washout 
After each period, there will be a three week washout period. Prior to discharge for each 
washout period, the following procedures will be performed: 
x Record concomitant medications 
x Monitor for AEs 
x Perform targeted physical exam 
x Measure vital signs (blood pressure, heart rate, respiratory rate, pulse oximetry, and 
oral body temperature) 
x Collect PK blood samples (6 mL) at timepoints specified in Section 4.7.1.1 
x Pre-discharge sedation assessment 
When subjects check-in after each washout period, the procedures and assessments 
specified in Section 4.6.4.1 will be performed. 
4.6.4.4 Discharge (or Early Termination) 


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The following procedures and assessments will be performed before a participant is 
discharged at the end of the study or at early termination: 
x Record concomitant medications 
x Monitor for AEs 
x Measure height, weight, and calculate body mass index 
x Perform clinical laboratory tests (hematology, serum chemistry, and urinalysis) 
x Measure vital signs (blood pressure, heart rate, respiratory rate, pulse oximetry and 
oral body temperature) 
x Collect PK blood samples (6 mL) at the timepoints specified in Section 4.7.1.1 (only 
day 21 of each study period) 
x Assess for pre-discharge sedation 
x Perform a safety 12-lead ECG  
x Perform a complete physical examination 
x Discharge subject from the study clinic after completion of all study procedures 
4.7 Study Procedures 
4.7.1 Pharmacokinetic Assessments 
4.7.1.1 Pharmacokinetic Sample Collection  
Pharmacokinetic blood samples will be collected on the following days and at the 
approximate times for each study period: 
x Day 5, 6, 11, 12, 20, and 21: 0 (pre-dose), 3, 4, 5, 8 hr (and 24 hrs for Day 6, 12, 
and 21) 
x Day 2 and 16: 0 (pre-dose), 2, 3, 4, 5, 6, 8, 12, 24 hr 
Blood samples will be collected by direct venipuncture or by inserting an IV catheter. 
There will be a total of 51 PK samples per participant for each study period (Total of 153 
PK samples per participant for the entire study duration). 
Each blood sample will be labeled with subject number, study number, study day, time 
point, event, and a barcode that matches that belonging to the subject. 
Collection of the PK samples on the ECG collection days (Days 2 and 16 of each period) 
will be time-matched to the ECG extractions; therefore, the subjects will be supine for 
approximately 10 minutes before the defined time points and for approximately 5 minutes 
after for ECG extraction/PK sample collection. The PK sample will be collected after the 


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ECG extraction to avoid changes in autonomic tone associated with the psychological 
aspects of blood collection and the reduction in blood volume subsequent to blood 
collection. A 5-minute window for PK sample collection is allowed after the ECG 
extraction window. 
4.7.1.2 Pharmacokinetic Specimen Handling 
The PK blood samples (6 mL each) will be collected into tubes containing K2EDTA, 
inverted several times to mix the blood with the anticoagulant, and placed in an ice bath. 
Within 30 minutes of collection, the samples will be centrifuged for 10 minutes, at 3000 
RCF, at 4°C, by a study team member. 
The plasma will be separated using a disposable plastic pipette and equally aliquoted into 
duplicate cryotube vials labeled as Aliquot A (primary) and Aliquot B (backup). The 
plasma samples will be appropriately labeled and stored frozen at -70°C or below within 
30 minutes after aliquoting until shipment. Temperature monitoring logs should be 
maintained and accessible for review by the study monitor.  
The Aliquot A samples (primary) will be shipped first, on dry ice, to the bioanalytical 
laboratory at FDA for processing when requested by the sponsor. The Aliquot B samples 
(backup) will be held for a second shipment after completion of all Aliquot A sample 
shipment(s) and the timing of the Aliquot B shipment will be communicated by the 
sponsor. None of the PK blood samples will be stored at the clinical facility for future 
use. 
4.7.1.3 Pharmacokinetic Parameters 
The following exploratory PK parameters will be determined for oxycodone and 
oxymorphone (days 6, 12, and 21) and paroxetine, escitalopram, and escitalopram 
metabolites (days 2, 5, 6, 11, 12, 16, 20, and 21): 
x Maximum observed plasma concentration (Cmax) 
x Area under the plasma concentration time curve (AUC) 
x Time at which Cmax occurs (Tmax) 
x Elimination rate constant (Kel) 
x Terminal half-life (t1/2) 
x Accumulation ratio (for escitalopram and paroxetine) 
4.7.2 Pharmacodynamic Assessments 
4.7.2.1 Duffin Rebreathing Assessments 


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Training on the Duffin’s rebreathing procedure will be performed to exclude any subjects 
who cannot tolerate the procedure.   
During Duffin’s rebreathing procedure, subjects will be placed in an upright position (90o 
angle) on a bed and connected to the respiration measurement set up. Subjects will wear a 
facemask and breathe from a pre-filled rebreathing bag containing approximately 5 L of 
either a hyperoxic-hypercapnic (24% O2, 6% CO2, N2 balanced) or hypoxic-hypercapnic 
(6% O2, 6% CO2, N2 balanced) gas mixture. During this study, subjects will be asked to 
breath room air for 5 minutes (relaxation stage) and then to hyperventilate (primarily 
through deep breathing) room air voluntarily for 5 minutes (hyperventilation stage). 
Thereafter, subjects will be switched to the rebreathing bag and perform rebreathing 
assessments at one of the 2 different isoxic end tidal PO2,  i.e., 150 mmHg or 50 mmHg. 
The isoxia at 150 mmHg or 50 mmHg end-tidal PO2 will be maintained by providing a 
computer controlled flow of 100% O2 to the rebreathing bag.   
Subjects will perform one hyperoxic and one hypoxic rebreathing procedure at check-in 
of each study period and a total of 4 rebreathing procedures (three hyperoxic and one 
hypoxic) each day on Days 5, 6, 11, 12, 20, and 21 of each study period. Rebreathing 
procedures will be performed while fasting and will occur at 0, 4, and 5 hours post-doses 
on assessment days (hyperoxic at 0, 4 and 5 hours; a hypoxic assessment will be 
performed after the 5 hour hyperoxic assessment). Participants can communicate to staff 
to discontinue an assessment due to discomfort at any time. Additional considerations for 
discontinuing a rebreathing procedure are described in a separate SOP for the 
Rebreathing Procedure. 
Each rebreathing procedure (relaxation, hyperventilation, and rebreathing) should take 
approximately 13-15 minutes. Data collected throughout the procedure includes 
ventilatory flow and volumes as well as percent gas compositions of O2 and CO2, which 
are used to calculate multiple physiological variables.  
Data from the rebreathing procedure will be acquired using the Hans Rudolph 
SmartLabTM Data Acquisition System. Collected data will be analyzed using separate 
statistical software. Interim data analyses may be performed after each cohort of 
participants have completed. If reproducibility is acceptable and no procedural changes 
are needed, additional lead-in cohorts may not be enrolled. If any study procedure 
element changes are needed, they may be made and additional participants may be 
enrolled.  
The clock on the rebreathing recorder will be confirmed to be consistent with the study 
clock at the clinical site; this will be confirmed on each study day. Preparatory steps for 
the Duffin’s rebreathing procedure (i.e., relaxation, hyperventilation) should begin prior 


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to the scheduled sample time. Timing of sample collection is planned so that the 
rebreathing assessment begins at the specified time. Additional details on the Duffin’s 
rebreathing procedure is described in a separate SOP.  
The following physiologic measurements will be assessed multiple times throughout the 
study: 
x Minute ventilation 
x Tidal volume 
x Respiratory rate 
x End-tidal PCO2  
x End-tidal O2 
x Oxygen saturation (SpO2) 
x Heart rate 
4.7.2.2 Pupillary Assessments 
At Screening, subjects will be evaluated to ensure they meet requirements necessary for 
pupillary assessments (e.g., pupils are reactive and not misshapen). During the study, a 
pupillometer (a hand-held optical scanner) will be used to measure pupil size and 
dynamics in response to a light stimulus. Pupillary assessments will be performed before 
and after each rebreathing period (except not in between the hyperoxic and hypoxic 
paired assessment) while the ambient light is kept to a consistent level. The rubber cup of 
the pupillometer will be placed on the right eye. The actual data recording only takes 
seconds.   
4.7.2.3 Sedation Assessments 
The Ramsey sedation scale will be completed by an observer prior to the start of 
rebreathing assessment. 
• 
Level 1: Patient awake, anxious and agitated or restless, or both 
• 
Level 2: Awake, cooperative, orientated, and tranquil 
• 
Level 3: Patient awake and responds to commands only 
• 
Level 4: Asleep, brisk response to light glabellar tap or loud auditory stimulus 
• 
Level 5: Asleep, sluggish response to light glabellar tap or loud auditory stimulus 
• 
Level 6: Asleep, no response to light glabellar tap or loud auditory stimulus 
At the same time as performing the Ramsey sedation scale, a visual analog scale will be 
administered to subjects by having subjects mark on a 100 mm perpendicular line how 
sedated they are from ‘awake and alert’ to ‘very sedated’ (i.e. 0 and 100 on the scale, 


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respectively). The distance from the left end of the line to the perpendicular mark will be 
measured in mm. 
4.7.2.4 ECG Assessments 
ECG assessments will be performed on the following study days and time of each study 
period: 
- Day 1: 0 (pre-dose) hr 
- Day 2 and 16: 0 (pre-dose), 2, 3, 4, 5, 6, 8, 12, 24 hr 
Ten second 12-lead ECG tracings with the most stable heart rate and highest signal-to-
noise ratio will be extracted in at least 3 replicates at ECG extraction time points during 
each treatment period. During all ECG extraction periods subjects will be placed in a 
supine position. Three ECG extractions will be performed for a baseline measurement 
before the first oral dose on day 1 of each treatment period. The other ECG 
extractions/period time matched to the PK samples will be obtained before the PK sample 
collection time. Subjects will be isolated (not able to see each other) in a quiet 
environment that is free from external stimuli. 
 
4.7.3 Safety Assessments 
Safety will be evaluated in terms of AEs, clinical laboratory results (hematology, serum 
chemistry, and urinalysis), vital sign measurements (blood pressure, heart rate, 
respiratory rate, and oral body temperature), safety 12-lead ECG results, and physical 
examination findings.  
4.7.3.1 Adverse Events 
4.7.3.1.1 Adverse Event Definitions 
An AE is defined as any untoward and/or unintended sign, including an abnormal clinical 
laboratory finding, symptom, or disease temporally associated with the use of a study 
drug, whether or not considered related to the study drug. Events or conditions that 
increase in frequency or severity during or as a consequence of use of a drug in human 
clinical trials will also be considered AEs. 
A treatment emergent adverse event (TEAE) is defined as an AE that begins after study 
drug administration. 
An unexpected AE is any AE having a specificity or severity not consistent with the 
current investigator’s brochure for the study drug(s). 


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A serious adverse event (SAE) is defined as any AE occurring at any dose that meets the 
following criteria: 
x Results in death, 
x Is life threatening, 
x Requires hospitalization or prolongation of existing hospitalization, 
x Results in persistent or significant disability or incapacity, 
x Results in a congenital anomaly/birth defect due to exposure prior to conception or 
during pregnancy, or 
x Is an important medical event that may not meet the previous criteria but, based upon 
appropriate medical judgment, jeopardizes the subject or requires medical or surgical 
intervention to prevent one of the outcomes listed previously. 
4.7.3.1.2 Adverse Event Reporting 
The recording of AEs will begin after the subject signs the informed consent form and 
will continue until discharge (or early termination). All AEs, whether serious or 
nonserious and whether or not related to the study drug, must be recorded in the eCRF. 
Study subjects will be instructed to warn study staff if he or she has any unexpected 
symptoms. In addition, all subjects will receive a reminder telephone call approximately 
24 h before Check-in. 
Any SAE (whether expected or unexpected) must be entered into the eCRF system and 
reported by email to the medical monitor or designee using the SAE Reporting Form 
within 24 h of the investigator or study clinic staff becoming aware of the event. It is the 
responsibility of the investigator to report all SAEs to the medical monitor, to provide the 
most complete report possible, and to assess each SAE for its relationship to the study 
drug. The investigator is responsible for obtaining follow-up information on all SAEs and 
submitting follow-up SAE data. Any unexpected SAEs must be reported promptly to the 
investigator’s IRB as per the IRB’s requirements. 
In the event of a fatal or life-threatening SAE, the sponsor will notify the appropriate 
FDA authorities within 7 calendar days of receipt of the report. The sponsor will follow 
all 7-day alert reports with a written report within 10 working days of receipt of the case. 
Serious AE cases that concern nonfatal, nonlife-threatening events that are unexpected 
and at least possibly related to the study drug will be submitted in writing to the FDA 
within 10 working days of receipt. 
Furthermore, any AEs that are not expected, occur at a higher frequency, or would 
require modification of the study protocol and/or informed consent must be reported to 
the FDA within 10 working days. 


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Adverse events that are assessed by the investigator as possibly or probably related to the 
study drug will be followed until they resolve or stabilize. All SAEs will be followed 
until resolution. 
4.7.3.1.3 Assessment of Severity 
The investigator will assess the severity of each AE using the following scale: 
x Mild: The subject is aware of the AE but is still able to perform all activities; minimal 
or no medical intervention or therapy is required. 
x Moderate: The subject has to discontinue some activities due to the AE; minimal or 
no medical intervention or therapy is required. 
x Severe: The subject is incapacitated by the AE and is unable to perform normal 
activities; significant medical intervention or therapy is required, and hospitalization 
is possible. 
4.7.3.1.4 Assessment of Causality 
The investigator will assess the causal relationship/relatedness of each AE to the study 
drug using the following scale: 
x Not Related: Onset of the AE has no reasonable temporal relationship to 
administration of the study drug, a causal relationship to administration of the study 
drug is biologically implausible, or the event is attributed to an alternative etiology. 
x Unlikely Related: Onset of the AE has a reasonable temporal relationship to study 
drug administration and although a causal relationship is unlikely, it is biologically 
plausible. 
x Possibly Related: Onset of the AE has a strong temporal relationship to 
administration of the study drug, cannot be explained by the subject’s clinical state or 
other factors, and a causal relationship is biologically plausible. 
x Probably Related: Onset of the AE shows a distinct temporal relationship to 
administration of the study drug that cannot be explained by the subject’s clinical 
state or other factors, the AE is a known reaction to the product or chemical group, or 
can be predicted by the product’s pharmacology. 
4.7.3.1.5 Pregnancy 
A serum pregnancy test will be performed for female subjects at the time points presented 
in the Schedule of Events (Appendix A). If a subject becomes pregnant while on the 
study, this should be reported immediately to the investigator, the subject will be 
withdrawn from the study and the medical monitor and the subject will be instructed to 


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follow-up with his or her personal physician. All pregnancies are to be reported as an AE 
and followed for outcome. 
4.7.3.2 Clinical Laboratory Tests 
Clinical laboratory and diagnostic screening tests will be performed at the time points 
presented in the Schedule of Event and will be collected in accordance with acceptable 
laboratory procedures. Clinical laboratory testing will be performed by the clinical study 
contractor(s). The clinical laboratory tests that will be performed are presented in Table 
4-3. Unused clinical laboratory test samples will not be stored for future use. 
Table 4-3: Clinical Laboratory Tests & Diagnostic Screening Tests 
Hematology 
Serum Chemistry 
Urinalysis 
Hematocrit 
Hemoglobin 
Platelet count 
Red blood cell count 
White blood cell count (with 
automated differential) 
Alanine aminotransferase 
Albumin 
Alkaline phosphatase 
Aspartate aminotransferase 
Bicarbonate 
Bilirubin (total, direct, and indirect) 
Blood urea nitrogen 
Calcium 
Chloride 
Creatinine (including calculated 
creatinine clearance) 
Glucose 
Lactate dehydrogenase 
Magnesium 
Phosphorus 
Potassium 
Sodium 
Total protein 
Uric acid 
Appearance 
Bilirubin 
Blood 
Color 
Glucose 
Ketones 
Leukocyte esterase 
Microscopic examination: red blood 
cells, white blood cells, epithelial cells, 
bacteria, crystals, and casts (if present) 
Nitrite 
pH 
Protein 
Specific gravity 
Urobilinogen 
Diagnostic Screening Tests: 
Serum 
Urine 
Whole Blood 
Serology (human 
immunodeficiency virus 
Ag/Ab Combo 1/2, hepatitis 
C virus antibody, and 
hepatitis B surface antigen) 
Female Subjects Only 
Human chorionic 
gonadotropin (for 
pregnancy) 
Follicle-stimulating 
hormone 
Drug screen including: 
amphetamines, barbiturates, 
benzodiazepines, cannabinoids, 
cocaine, alcohol, opiates, 
phencyclidine, propoxyphene, 
methadone, and cotinine 
Cytochrome P450 2D6 genotype (only 
performed at check-in for the first 
study period) 
 
Other 
SARS-CoV2 rapid antigen test  


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Clinical laboratory results will be reviewed by the investigator or designee together with 
data in the eCRF. Any values outside the reference range will be evaluated for clinical 
significance. If a value is determined to be clinically significant, the subject will be 
instructed to follow-up with his or her personal physician. The investigator or designee 
may repeat the clinical laboratory tests if deemed appropriate. The investigator will 
maintain a copy of the laboratory accreditation and the reference ranges for the laboratory 
used. 
4.7.3.3 Vital Sign Measurements 
Vital signs (blood pressure, heart rate, respiratory rate, and oral body temperature) will be 
measured using an automated device at the time points presented in the Schedule of 
Events (Appendix A). The subject should be in a supine position, if possible, for a 
minimum of 5 minutes before vital signs are measured.  
4.7.3.1 Pulse Oximetry 
Continuous pulse oximetry monitoring will be performed on rebreathing days (Days 5, 6, 
11, 12, 20, and 21 of each study period) specified in the Schedule of Events (Appendix 
A). 
4.7.3.2 Safety 12-lead Electrocardiograms 
Safety 12-lead ECGs will be obtained with the subjects in the supine position for a 
minimum of 10 minutes before recording. ECGs will be overread by the Principal 
Investigator or designee (e.g., a medically qualified subinvestigator). If an abnormality is 
observed, the subject will be instructed to follow-up with his or her personal physician. 
4.7.3.3 Physical Examinations 
A complete physical examination will be performed at the time points presented in the 
Schedule of Events (Appendix A). 
The complete physical examination will include, but not be limited to, assessments of the 
head, eyes, ears, nose, throat, skin, thyroid, nervous system, respiratory system, 
cardiovascular system, abdomen (liver and spleen), lymph nodes, and extremities. 
Height, weight (without shoes and wearing the lightest possible clothing), and calculation 
of body mass index will be performed at Screening and check-out. 
If a clinically significant abnormality is observed upon physical examination, the subject 
will be instructed to follow-up with his or her personal physician. 
4.7.4 Demographics and Medical History 
Demographic data (date of birth, gender, race, and ethnicity) will be collected at 
Screening. 


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Each subject will provide a complete medical history at Screening that will be reviewed 
at Check-in. Specific information relating to any prior or existing medical 
conditions/surgical procedures will be recorded in the subject’s eCRF. 
4.8 Study Treatments 
4.8.1 Dose Strategy  
Prior data with oxycodone alone using 20 mg doses, showed significant decreases in 
VE55 from baseline.5-6 Our previous study that administered 10 mg oxycodone showed 
approximately 5 L/min decrease with oxycodone alone compared to baseline.20 The goal 
with the oxycodone dose is to have an effect on the hypercapnic ventilatory response with 
oxycodone alone, but not too high (for safety considerations) as it will be combined with 
a SSRIs that may also have effects on ventilation.  
Paroxetine dosing in labeling starts at 20 mg/day and allows titration up to a maximum of 
60 mg/day for obsessive compulsive disorder (panic disorder starts at 10 mg/day and 
allows titration up to 60 mg/day). Dosing to 60 mg/day will allow assessment of effects 
on ventilation alone or combined with oxycodone under clinically relevant exposures 
Escitalopram dosing in labeling starts at 10 mg/day and allows titration up to 20 mg/day 
for treatment of major depressive disorder and treatment of generalized anxiety disorder. 
The study will administer up to 30 mg/day, which is above the maximal labeled dose of 
escitalopram (20 mg/day), but doses up to 30 mg/day have been evaluated in a thorough 
QT study. Escitalopram exposure with 30 mg/day is similar to the steady state 
concentration expected in CYP2C19 poor metabolizers following a therapeutic dose of 
20 mg/day. 
4.8.2 Treatments Administered  
For all drugs, standard drug doses or doses used in prior studies in healthy participants 
will be used in this study. Multiple doses of the assigned study drug will be administered 
to each subject during the treatment period. Oxycodone, paroxetine, escitalopram, 
ondansetron, and placebo will be administered orally. Subjects will complete each of the 
three treatments (A, B, and C):  
x Treatment A: Placebo on Days 1-5; Placebo + Oxycodone (10 mg IR) on Day 6; 
Placebo on Days 7-11; Placebo + Oxycodone (10 mg IR) on Day 12; Placebo on 
Days 13-20; Placebo + Oxycodone (10 mg IR) on Day 21 
x Treatment B: Paroxetine (40 mg) on Days 1-5; Paroxetine (40 mg) + Oxycodone (10 
mg IR) on Day 6; Paroxetine (60 mg) on Days 7-11; Paroxetine (60 mg) + 
Oxycodone (10 mg IR) on Day 12; Paroxetine (60 mg) on Days 13-20; Paroxetine (60 
mg) + Oxycodone (10 mg IR) on Day 21 


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x Treatment C: Escitalopram (20 mg) on Days 1-5; Escitalopram (20 mg) + Oxycodone 
(10 mg IR) on Day 6; Escitalopram (30 mg) on Days 7-11; Escitalopram (30 mg) + 
Oxycodone (10 mg IR) on Day 12; Escitalopram (30 mg) on Days 13-20; 
Escitalopram (30 mg) + Oxycodone (10 mg IR) on Day 21 
Paroxetine, escitalopram, or placebo will be administered at time 0 on each day. 
Oxycodone dosing will occur at 3 h on days 6, 12, and 21. Participants will also receive 
ondansetron 4 mg 30 min before oxycodone administration on days 6, 12, and 21. 
Study drugs will be administered by a clinical research nurse on the study clinic floor at 
the subject’s bedside. The pharmacist and investigator will be available if needed during 
study drug administration. Oral study drugs will be administered with 240 mL of 
room-temperature water. 
4.8.3 Dose Selection and Schedule 
Oxycodone: The oxycodone dose is 10 mg IR. Oxycodone dose selection is based on 
previous published results where oxycodone was administered alone or in combination 
using rebreathing procedures in healthy volunteers. Two studies by van der Schrier and 
others evaluated oxycodone 20 mg alone or in combination with ethanol.5-6 Sedation 
levels in the ethanol study in particular, which included a higher dose of oxycodone and 
was performed in the young and elderly, were moderate and well addressed by mild 
stimulation of the subjects. Varying dose combinations of oxycodone and morphine (total 
combined doses of 15 mg) have been safely evaluated using a similar system.7 Our 
previous study with oxycodone 10 mg IR showed that small (approximately 5 L/min) but 
detectable effects on hypercapnic ventilation could be safely observed with this dose with 
minimal effects on baseline ventilation.20   
Paroxetine: The paroxetine dose is 40 mg IR for Days 1-6 and 60 mg IR for Days 7-21. 
Paroxetine dose selection was based on available safety data from the original 
development program and to achieve sustained steady state exposures of paroxetine at the 
highest approved paroxetine dose for at least one week before the day 20 and 21 
assessments.  Target dosing range for paroxetine is 20-60 mg/day depending on the 
indication. Initial starting doses in labeling for general anxiety disorder, social anxiety 
disorder, posttraumatic stress disorder, obsessive compulsive disorder, and major 
depressive disorder are 20 mg/day with dose increases of 10-mg/day made in intervals of 
1 week. Paroxetine has been administered at 30 mg/day for 30-days in healthy volunteers 
and up to 60-mg as a single dose in healthy volunteers.51  
Escitalopram: The escitalopram dose is 20 mg for Days 1-6 and 30 mg for Days 7-21. 
Escitalopram dosing in labeling starts at 10 mg/day and allows titration up to 20 mg/day 
for treatment of major depressive disorder and treatment of generalized anxiety disorder. 
The study will administer up to 30 mg/day, which is above the maximal labeled dose of 


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escitalopram (20 mg/day), but doses up to 30 mg/day have been evaluated in a thorough 
QT study for a comparable duration of time. Escitalopram exposure with 30 mg/day is 
similar to the steady state concentration expected in CYP2C19 poor metabolizers 
following a therapeutic dose of 20 mg/day.55 
Ondansetron: The ondansetron dose is 4 mg orally given 30 minutes before oxycodone 
administration. Up to two additional doses of IV ondansetron 4 mg can be given in a day 
for nausea/vomiting. The selected ondansetron dose is less than the recommended dosing 
for labeled indications of nausea and vomiting associated with highly or moderately 
emetogenic cancer chemotherapy, radiotherapy, or postoperative nausea or vomiting.  
Naloxone: The naloxone dose is 0.4 mg administered intravenously, as needed, for 
respiratory depression as deemed necessary by the investigator. Naloxone may be 
administered as a rescue medication for opioid-induced respiratory depression. 
4.8.4 Method of Assigning Subjects to Treatment Sequence 
4.8.4.1 Randomization Process 
The project biostatistician will create the specifications that will be used to generate the 
randomization schedule. The specifications will be based on the protocol requirements 
and appropriate statistical programming with consideration for study design, number of 
treatments, number of subjects planned for enrollment, stratification, and blocking. 
Based on these specifications, the project biostatistician (or designee) will generate a 
dummy randomization schedule. The schedule is generated in R.  
The project biostatistician (or designee) distributes the ‘dummy’ randomization schedule 
to specified personnel for review. Any change (e.g., change in block size, change in 
stratification levels) that requires an update to the specifications will reset this process. 
Minor changes (e.g., display formatting) will not require a change to the specifications. 
After the approval of the ‘dummy’ randomization schedule, the project biostatistician (or 
designee) transfers the program used to generate the ‘dummy’ schedule to the 
randomization biostatistician (unblinded), who is an independent party and will not be 
participating in any programming or statistical decisions for the study before breaking the 
blind. No transfer is necessary if the unblinded randomization biostatistician also created 
the ‘dummy’ randomization. 
The randomization biostatistician is responsible for generating the final randomization 
schedule. The output is sent only to designated unblinded recipients, who will maintain a 
secured digital and printed copy for their use. 


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Archival of the programs and output is accomplished by the creation of an encrypted, 
password-protected ZIP file containing the program and output file(s). The ZIP file is 
copied to a secure storage drive on the sponsor’s site. 
Randomization will occur after informed consent is obtained, either after completion of 
check-in procedures on Day -1 or just before dosing on Day 1. Approximately 25 healthy 
male and female subjects are planned for enrollment. Thus, a maximum of 25 subjects 
will be exposed to study drugs and procedures during the study. 
Enrolled subjects will be randomly assigned to 1 of 6 different treatment sequences 
consisting of the treatment groups are presented in Table 4-2. 
All randomization information will be secured and housed in a locked storage area, 
accessible only by the randomization personnel and the assigned pharmacist and his or 
her verifier. 
4.8.5 Identity of Study Drugs 
Oxycodone HCl (referred to throughout this document as oxycodone) is indicated for the 
management of pain severe enough to require an opioid analgesic and for which 
alternative treatments are inadequate. Oxycodone tablets are available as 5, 10, 15, 20, or 
30 mg strengths. The tablets are designed for immediate release of the drug where about 
60% to 87% of the drug reaches systemic circulation in comparison to a parenteral dose. 
Oxycodone HCl has a molecular weight of 351.82 and the molecular formula 
C18H21NO4ƔHCl. The physical form is a white odorless crystalline powder derived from 
the opium alkaloid, thebaine. Oxycodone dissolves in water (1 g in 6 to 7 mL) and is 
considered slightly soluble in alcohol.53 
Paroxetine HCl (referred to throughout this document as paroxetine) is indicated for the 
treatment of major depressive disorder. Paroxetine HCl has a molecular weight of 374.8 
and the empirical formula is C19H20FNO3Ɣ+&OƔ1/2H2O. Paroxetine HCl is an odorless, 
off-white powder with a solubility of 5.4 mg/mL in water. Tablets are available for oral 
administration in 10, 20, 30, and 40 mg strengths.48  
Escitalopram oxalate (referred to throughout this document as escitalopram) is indicated 
for acute and maintenance treatment of major depressive disorder and acute treatment of 
generalized anxiety disorder. Escitalopram is the pure S-enantiomer of the racemic 
bicyclic phthalane derivative citalopram. Escitalopram oxalate has a molecular weight of 
414.4 and the empirical formula is C20H21FN2OƔC2H2O4. Escitalopram oxalate is a fine, 
white to slightly-yellow powder and is freely soluble in methanol and dimethyl sulfoxide, 
soluble in isotonic saline solution, sparingly soluble in water and ethanol, slightly soluble 
in ethyl acetate, and insoluble in heptane. Tablets are available for oral administration in 
5, 10, and 20 mg strengths.49 


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Ondansetron is indicated for the prevention of nausea and vomiting associated with 
highly emetogenic cancer chemotherapy, including cisplatin greater than or equal to 50 
mg/m2, initial and repeat courses of moderately emetogenic cancer chemotherapy, 
radiotherapy in patients receiving either total body irradiation, single high-dose fraction 
to the abdomen, or daily fractions to the abdomen, and prevention of postoperative 
nausea and/or vomiting. The empirical formula is C18H19N3OƔHClƔ2H2O, 
representing a molecular weight of 365.9. Ondansetron hydrochloride dihydrate is a 
white to off-white powder that is soluble in water and normal saline. Ondansetron is 
available for oral administration as 4 and 8 mg tablets. Ondansetron hydrochloride is 
supplied as 20 mL multi-dose vials, 2 mg/mL.56 
Naloxone hydrochloride injection is indicated for the complete or partial reversal of 
opioid depression, including respiratory depression, induced by natural and synthetic 
opioids. Naloxone hydrochloride is also indicated for the diagnosis of suspected or 
known acute opioid overdosage. Naloxone hydrochloride, an opioid antagonist, is a 
synthetic congener of oxymorphone, with a molecular weight of 363.84 and molecular 
formula of C19H21NO4ƔHCl. Naloxone hydrochloride injection may be diluted for 
intravenous infusion in 0.9% sodium chloride injection or 5% dextrose injection. The 
addition of 2 mg of naloxone hydrochloride in 500 mL of either solution provides a 
concentration of 0.004 mg/mL. Mixtures should be used within 24 h. After 24 h, the 
remaining unused solution must be discarded. Naloxone hydrochloride injection is 
supplied as 10 mL multi-dose vials, 4 mg/10 mL (0.4 mg/mL).52  
Placebo capsules containing only cornstarch will be used as the placebo oral control in 
this study. 
4.8.6 Management of Clinical Supplies 
4.8.6.1 Study Drug Packaging and Storage 
The active study drugs will be obtained from commercial sources. Storage instructions 
for the active study drugs are as follows: 
x Oxycodone tablets should be stored at 25°C (77°F) with excursions permitted 
from 15° to 30°C (59° to 86°F) and should be protected from moisture.53  
x Paroxetine tablets should be stored between 15° and 30°C (59° and 86°F).54 
x Escitalopram tablets should be stored between 20° and 25°C (68° and 77°F); 
excursions permitted to 15° and 30°C (59° and 86°F).55 
x Naloxone hydrochloride injection should be stored at 20° to 25°C (68° to 77°F).58 
x Ondansetron tablets should be stored at 2° to 30°C (36° to 86°F).56  


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x Ondansetron injection should be stored at 20° to 25°C (68° to 77°F).59 
Placebo capsules will be supplied by the clinical site, stored at controlled room 
temperature (15°C to 30°C; 59°F to 86°F), and protected from light and moisture. 
4.8.6.2 Study Drug Accountability 
Good clinical documentation practices will be employed to record the receipt, storage 
conditions, accountability, and use or return of the study drug. The study drug will be 
stored in a secure location with access to the study personnel who will be managing the 
storage, dispensing, and accountability of the study drug. 
Upon completion or termination of the study, final accountability review by the study 
monitor, and written authorization from the sponsor, all unused and/or partially used 
study drug should be returned or destroyed at the study clinic. It is the investigator’s 
responsibility to ensure that the sponsor has provided written authorization for study drug 
disposal, the disposal process follows the study clinic’s standard operating procedures, 
and appropriate records of the disposal are documented and maintained. No unused study 
drug may be disposed until fully accounted for by the study monitor (or designee). 
Documentation of unused study drug should include subject number, medication identity 
(medication #, period #), date, and quantity of study drug used. 
4.8.7 Blinding 
The study will be double-blind, and the blind will be maintained through a randomization 
schedule held by the dispensing pharmacist. Treatments (escitalopram, paroxetine, or 
placebo) will be over-encapsulated. The pharmacist (and designated staff member 
responsible for confirmation of study drug dose) will be unblinded to subject treatment 
assignment; however, the pharmacist will not perform any study procedures other than 
study drug preparation and dispensing.  
 
Additional details regarding blinding can be found in the Spaulding Blinding SOP which 
will be followed to ensure the blind is maintained throughout the study. 
4.8.7.1 Breaking the Blind 
The study drug blind will not be broken by the investigator or designee unless 
information concerning the study drug is necessary for the medical treatment of the 
subject. For unblinding a subject, the randomization information for unblinding can be 
obtained by contacting the dispensing pharmacist. The sponsor or medical monitor must 
be notified immediately if the study drug blind is broken. The date, time, and reason that 
the blind was broken will be recorded in the source documents. If the blind is broken by 
the investigator or designee, the study drug must be stopped immediately, and the subject 


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must be withdrawn from the study. Data or specimens already collected from subjects 
who discontinue prematurely and for whom the blind is broken will be made available for 
analysis if needed. 
4.8.8 Treatment Compliance 
At Screening, as part of the inclusion criteria, it will be confirmed that subjects are able to 
comply with the protocol-defined procedure of injecting subcutaneous study drug. All 
doses of the study drug will be administered in the study clinic either under direct 
observation of or administered by clinic personnel and recorded in the eCRF. If a subject 
vomits after dosing, the event will be documented as an AE. The decision to replace any 
subject who vomits after dosing will be made as described in Section 4.5.1. 
4.8.9 Prior and Concomitant Medications 
Subjects are prohibited from using any prescription or nonprescription drugs (including  
aspirin or NSAIDs and excluding oral contraceptives and acetaminophen) within 14 days 
or 5 half-lives (whichever is longer), or complementary and alternative medicines within 
28 days before the first dose of study drug. Subjects are prohibited from using any opioid 
or psychotropic drugs within 60 days of the start of the study. Subjects will be asked if 
they have used any of these substances and their responses will be recorded on the eCRF. 
Subjects are also prohibited from currently participating in another clinical study of an 
investigational drug and may not have been treated with any investigational drug within 
30 days or 5 half-lives (whichever is longer) of the compound. 
Subjects must be instructed not to take any medications, including over-the-counter 
products, without first consulting with the investigator. 
4.8.10 Subject Restrictions 
Subjects are not allowed to use nicotine containing products (e.g., cigarettes, cigars, 
chewing tobacco, snuff, electronic cigarettes) within 6 weeks before Screening. In 
addition, subjects are not allowed to ingest alcohol, xanthine containing products (e.g., 
tea, coffee, chocolate, cola), caffeine, grapefruit, or grapefruit juice within 24 h of check-
in of all study periods. Subject must refrain from ingesting these throughout the entire 
study. Subjects are not allowed to use aspirin or NSAIDs within 14 days before the first 
dose of study drug. Subjects will be asked if they have used any of these substances and 
their responses will be recorded on the eCRF. 
Subjects must be able to tolerate a controlled, quiet study conduct environment, including 
avoidance of music, television, movies, games, and activities that may cause excitement, 
emotional tension, or arousal during prespecified times (e.g., before and during ECG 


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extraction windows; before and during rebreathing procedures) throughout the duration 
of the study. 
Subjects must be willing to comply with study rules; attempting to void at specified 
times; remaining quiet, awake, undistracted, motionless, and supine during specified 
times; and avoiding vigorous exercise as directed throughout the duration of the study. 
Standardized meals will be served at consistent times relative to dosing, and no food or 
fluids will be served containing caffeine. Subjects will fast during days with rebreathing 
assessments (i.e., Day 5, 6, 11, 12, 20, and 21 of each period) until after the last 
rebreathing assessment. On ECG collection days (Day 2 and 16 of each period) subjects 
will have fasted for at least 8 hours prior to drug administration. Subjects should only eat 
meals and snacks that are provided during periods of their stay in the study clinic, and 
should consume each meal that is served at a reasonable pace (within 25 minutes). 
Outside of meal times, the subjects will only be allowed to intake water, which will be 
available ad libitum. 
Due to current precautions being taken for COVID-19, the following restrictions will be 
in place: 
x Subjects should be encouraged to wear masks except when in a private room without 
anyone else present or for a limited time for a study procedure (e.g., study drug 
administration or eating) when instructed by staff.  
x Subjects must practice social distancing, which will include having a maximum of 2 
subjects per room for overnight stays and access to common areas will be per clinical 
research site standards. While subjects are in house,  meals will be served per clinical 
research site standards. Subjects will spend most of their time in their rooms except 
for specified times for walking in the halls (with masks recommended). 
x Subjects must practice regular handwashing with soap and water, scrubbing hands for 
at least 20 seconds or with approved hand sanitizer as supplied by study staff.  
Designated isolation rooms will be set up to segregate any participant(s) that develop any 
symptoms of concern while housed in the unit and COVID-19 testing will be done when 
deemed necessary by the Investigator. If new information becomes available, there could 
be other precautions that lead to additional restrictions that will be documented in the 
COVID-19 Risk Management Plan and/or the study specific COVID-19 Procedure Plan. 
4.9 Statistical Methods 
4.9.1 Sample Size 
Approximately 25 healthy participants are planned for enrollment. A previous study (20 
participants) with paroxetine showed a decrease in 10.2 L/min in VE55 for paroxetine (40 


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mg) combined with oxycodone (10 mg) compared to oxycodone alone after 5 days of 
dosing with paroxetine. Similarly, there was a 9.3 L/min decrease in paroxetine compared 
to placebo after 4 days of dosing with paroxetine. The standard deviation in assessments 
was approximately 6.5 L/min. Assuming a similar effect size with paroxetine and 
escitalopram at day 20 and 21, the planned number of participants allows for a 40% drop 
out rate while maintaining at least 90% power for separate one-sided tests at a 0.025 
significance level with the multiple primary endpoint. Study sample size did not consider 
secondary endpoints. 
4.9.2 Analysis Populations 
The rebreathing analysis population will include all subjects who completed at least one 
rebreathing assessment on any day or at any timepoint. Specific information on analysis 
populations for different pharmacodynamic measures will be described in the Statistical 
Analysis Plan (SAP).  
A rebreathing assessment will be considered complete if the subject makes it through the 
entire procedure at a specific timepoint, if there are no identifiable issues with how the 
procedure was conducted, and if the VE55 regression converges.  Potential issues with 
how the procedure was conducted can included, but are not limited to, a leak from the 
system (e.g., substantially decreasing O2 during rebreathing or no evidence of an increase 
in CO2 during rebreathing) or inaccurate readings from the pneumotach (e.g., baseline 
minute ventilation readings less than 5 L/min).  
Subjects in this population will be used for the planned primary and secondary analyses 
related to evaluating drugs effects on the ventilatory response to hypercapnia.  If a subject 
does not contribute data from all treatments due to early discontinuations or other reasons, 
only those comparisons where the subject has all required data will be performed. 
The PK population will include all subjects who receive study drug and have at least 
one estimable PK parameter after dosing. 
The safety population will include all subjects who receive at least one dose of any of the 
study drugs. 
4.9.3 General Statistical Considerations 
All data will be presented in data listings. Data from subjects excluded from an analysis 
population will be presented in the data listings, but not included in the calculation of 
summary statistics. Demographic and baseline characteristics will be summarized overall 
and by treatment for all subjects. 
4.9.4 Subject Disposition 


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The number of subjects who enroll in the study and the number and percentage of 
subjects who complete each assessment will be presented. The frequency and percentage 
of subjects who withdraw or discontinue from the study and the reason for withdrawal or 
discontinuation will be summarized. 
4.9.5 Demographics and Baseline Characteristics 
Descriptive statistics will be used to summarize demographic and baseline subject 
characteristics. For continuous variables, the mean, median, standard deviation (SD), 
minimum, and maximum values will be reported. For categorical (nominal) variables, the 
number and percentage of subjects (or observations) will be reported. 
4.9.6 Rebreathing Analyses 
4.9.6.1 Primary Analysis  
The primary objective is to study ventilatory effects of SSRIs (paroxetine or 
escitalopram) combined with an opioid (oxycodone) compared to an opioid alone. The 
primary endpoint is VE55 under hyperoxic conditions on day 21.  
4.9.6.2 Data Analysis  
Minute ventilation and end-tidal pCO2 (PETCO2) data from the rebreathing stage of the 
Duffin rebreathing procedure will be analyzed at the specified primary timepoints using 
piecewise linear regressions. The regressions will be used to predict VE55. VE55 when 
the SSRIs (paroxetine or escitalopram) are combined with oxycodone will be compared 
to VE55 with oxycodone alone.  
Multiple primary analyses are planned for each drug. The first primary analysis will be 
VE55 on day 21 at 5 h (hyperoxic) between oxycodone with paroxetine or escitalopram 
compared to oxycodone alone. The second primary analysis will be VE55 on day 20 at 5 h 
(hyperoxic) between paroxetine or escitalopram compared to placebo. Since Day 20 and 
21 are considered multiple primary endpoints, comparisons will have an adjustment for 
multiplicity using a Bonferroni correction (each day will be tested at a 0.025 significance 
level). No adjustments will be made for separate testing of paroxetine or escitalopram since 
the treatments are considered separate interventions in the study.  
A linear mixed effects model will be developed using all study data from hyperoxic 
assessments. Fixed effects will include treatment, period, sequence, and baseline VE55 
(i.e., VE55 obtained at 0 h on Day -1 of each treatment period).  Subject will be included 
as a random effect on the intercept.  If a subject’s baseline VE55 for a treatment period is 
not available, then the baseline value for that period will be calculated based on the median 
of all other baseline values for that subject from other study periods.  If a subject does not 


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have any completed baseline VE55 data, the subject will be assigned a baseline VE55 equal 
to the median of the population.  
The Kenward-Roger approximation will be used to estimate denominator degrees of 
freedom for tests of  fixed effects. Normality assumption will be verified using the Shapiro-
Wilke test for normality. Homogeneity of variances will be verified using Levene’s test. If 
the data in its original or transformed form does not satisfy assumptions for normality and 
homogeneity, a Wilcoxon signed-rank test will be used for all comparisons rather than a 
linear mixed effect model. In the event that the data does not satisfy assumptions for 
normality and homogeneity then a Wilcoxon signed-rank test will be used for comparisons.  
To demonstrate an effect when an SSRI (paroxetine or escitalopram) is combined with 
oxycodone compared to oxycodone alone, the upper bound of the one-sided 97.5% CI of 
the least-square mean VE55 difference between treatments must not overlap 0 L/min.  
Similarly, to demonstrate an effect of paroxetine (or escitalopram) compared to placebo 
the upper bound of the one-sided 97.5% CI of the least-square mean VE55 difference 
between treatments must not overlap 0 L/min. Each comparison will be performed 
separately (i.e.,þtrt’ asþparoxetine’ orþescitalopram’):  
ЬH0: VE55oxy+trt - VE55oxy  0 L/min 
ЬHA: VE55oxy+trt - VE55oxy < 0 L/min 
For secondary endpoints, effects of SSRIs (paroxetine or escitalopram) with oxycodone 
compared to oxycodone alone will be performed on day 6 and day 12. 
As additional secondary endpoints, effects of SSRIs (paroxetine or escitalopram) alone 
compared to placebo will be determined on day 5 and 11 using the same model. Additional 
details on testing of ventilation secondary endpoints is discussed in the SAP. 
4.9.7 Pharmacokinetic Analysis 
The PK parameters Cmax, AUC0-t, Tmax, and Kel will be summarized using descriptive 
statistics (number of subjects, geometric mean, coefficient of variation [CV], mean, SD, 
median, minimum, and maximum) on Day 2, 5, 6, 11, 12, 16, 20 and 21 of each period 
for paroxetine, escitalopram, and escitalopram metabolites (Days 6, 12, and 21 for 
oxycodone and oxymorphone). The PK parameters will be analyzed using 
noncompartmental methods based on actual sampling times. Geometric mean and 
individual concentration-time profiles will be presented in graphs. 
4.9.8 PK/PD Modeling 
A nonlinear-mixed effect pharmacokinetic/pharmacodynamic model will be developed 
for VE55 and baseline-adjusted VE55 versus time for all treatments. The model will be 
developed using modeling software.  


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Additional details on PK/PD modeling will be discussed in a separate Modeling Analysis 
Plan. 
4.9.9 Electrocardiogram Analyses 
The QT interval will be corrected for heart rate using Fridericia’s formula 
(QTc=QT/RR1/3). The J-Tpeak interval will be corrected for heart rate using the formula 
(J-TpeakC = J-TpeakC/RR0.58).60 Baseline will be the mean of the 3 predose ECG extractions 
of Day 1. 
Exposure-response analyses will be performed for the change-from-baseline in QTc 
ǻ47FDQGFKDQJH from baseline in other ECG measurements (specified in ECG 
Analysis Plan), where the mean of the 3 predose ECG readings on Day 1 will be used as 
the Baseline. The concentration of the drug will be used as a covariate. Exposure-
response analysis will be done following most recent best practices in concentration-QTc 
modeling.61-62  
To assess the appropriateness of a linear model, normal QQ-plots for the residuals and 
plots of weighted residuals versus concentration and versus fitted values will be 
produced. A model with a quadratic term in concentration will be fitted and the quadratic 
term will be tested on the 2-sided 5% alpha level. In case of a significant quadratic term, 
nonlinear models, such as a log-linear model and an Emax model, will be investigated and 
the primary model will be selected based on the Akaike Information Criterion and 
plausibility arguments.  
Unless the prespecified test procedure for linearity indicates otherwise, the primary 
analysis will be based on a linear mixed effects model implemented in R software, with 
ǻ47FDVWKHGHSHQGHQWYDULDEOHGUXJSODVPDFRQFHQWUDWLRQDQGEDVHOLQH47FDV
continuous covariates, treatment and time point as categorical factors, and subject 
specific random effects for the intercept and slope. All post dose data will be used. The 
degrees of freedom for the model estimates will be determined by the Kenward-Rogers 
method. From the model, the slope (i.e., the regression parameter for the concentration) 
and the treatment effect will be estimated together with 2-sided 90% CIs. 
The predicted mean placebo-adjusted change from baseline QTc (ǻǻQTc) at the 
observed geometric mean Cmax LHWKHSURGXFWZLWKWKHVORSHHVWLPDWHௗௗWUHDWPHQWHIIHFW
[ǻQTcactive – ǻQTcplacebo]) and the 2-sided 90% CI of the estimate will be calculated.  
Additional details will be specified in the ECG Analysis Plan, including for analysis of 
other ECG measurements. 
 
4.9.10 Additional Analyses  


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4.9.10.1 Exploratory Respiratory Analyses  
Baseline minute ventilation, ventilatory recruitment threshold, slope of the PCO2-
ventilatory response curve, and the extrapolated ventilatory recruitment threshold will be 
calculated for each subject at each rebreathing assessment. Data collected during the 
Duffin Rebreathing procedure will be used to determine the slope of the minute 
ventilation / PETCO2 regression line.  Resting ventilation, tidal volume, end-tidal PCO2, 
and oxygen saturation will be determined using data from the relaxation portion of the 
Duffin Rebreathing procedure.  Apneic events lasting > 10 s will be determined using 
data collected during relaxation and preparation portion of the Duffin Rebreathing 
procedure.  An event is defined as the absence of inspiratory flow (as measured by the 
pneumotachograph) for at least 10 s during this period.  These parameters will be 
summarized using descriptive statistics, and time courses summaries will be generated for 
all treatment groups. Differences in hypercapnic ventilatory response under hyperoxic or 
hypoxic rebreathing at the 5-h timepoint will be performed using paired t-test. These 
analyses will be considered hypothesis-generating and exploratory. 
4.9.10.2 Pupillometry Analyses  
Maximum pupil diameter before constriction and dynamic pupillary measurements after a 
light stimulus will be measured before and after each rebreathing assessment (except not 
in between the hyperoxic and hypoxic paired assessment). These parameters will be 
summarized using descriptive statistics, and time courses summaries of both scores will 
be generated for all treatment groups.  Pupillary changes will be compared to baseline 
measurements and between treatments to evaluate the effect of different interventions on 
pupillary changes.  In addition, time course pupillary changes will be compared to time 
course ventilatory changes across treatments to evaluate concordance between these 
measures when subjects receive different drugs and drug combinations. These analyses 
will be considered hypothesis-generating and exploratory. 
4.9.10.3 Sedation Scores Analyses  
Ramsay Sedation Scale is an observer-based assessment of sedation that will be collected 
for each subject as during the relaxation period of each Duffin Rebreathing procedure.  In 
addition, subjects will be asked to provide their own assessment of sedation using the 
Visual Analog Scale during the same relaxation period. These are two measures for 
assessing an individual’s level of sedation and will provide a subjective assessment of 
how sedation the subject is experiencing during the study.  These parameters will be 
summarized using descriptive statistics, and time courses summaries of both scores will 
be generated for all treatment groups. These analyses will be considered 
hypothesis-generating and exploratory. 


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4.9.11 Safety Analyses 
4.9.11.1 Adverse Events 
All AEs will be coded using the latest version of the Medical Dictionary for Regulatory 
Activities. The incidence of TEAEs, organized by system organ class and frequency, will 
be summarized by seriousness, severity, relationship to treatment, and by treatment at 
onset of the TEAE. A detailed listing of serious AEs and TEAEs leading to withdrawal 
will also be provided. 
4.9.11.2 Clinical Laboratory Tests 
Clinical laboratory results will be reviewed by the investigator or designee together with 
data in the eCRF. Any values outside the reference range will be evaluated for clinical 
significance. If a value is determined to be clinically significant, the subject will be 
instructed to follow-up with his or her personal physician. The investigator or designee 
may repeat the clinical laboratory tests if deemed appropriate. The investigator will 
maintain a copy of the laboratory accreditation and the reference ranges for the laboratory 
used. 
Clinical laboratory results (hematology, serum chemistry, and urinalysis) will be 
summarized using descriptive statistics (number of subjects, mean, SD, minimum, 
median, and maximum). Clinical laboratory results will be classified as normal or 
abnormal, according to the reference ranges of the individual parameter. The number and 
percentage of subjects with abnormal laboratory results will be provided. No statistical 
testing will be performed on clinical laboratory data. 
4.9.11.3 Vital Sign Measurements 
Vital sign measurements and changes from Baseline will be summarized using 
descriptive statistics (number of subjects, mean, SD, minimum, median, and maximum) 
by treatment and time point. 
4.9.11.4 Pulse Oximetry 
Continuous pulse oximetry will be performed on rebreathing days. Events requiring 
intervention from the staff or discontinuation from the study will be recorded in 
appropriate logs. 
4.9.11.5 Safety 12-lead Electrocardiograms  
12-lead ECGs will be obtained with the subjects in the supine position for a minimum of 
5 minutes before recording. ECGs will be overread by a physician. If an abnormality is 
observed, the subject will be instructed to follow-up with his or her personal physician. 


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4.9.11.6 Physical Examinations 
 Physical examination findings will be presented in a data listing, and abnormal physical 
examination findings will be recorded as AEs. 
4.9.11.7 Other Safety Data 
All concomitant medication usage and medications that changed in daily dose, frequency, 
or both since the subject provided informed consent will be summarized for each subject. 
4.9.12 Interim Analyses 
No interim analyses are planned. 
4.9.13 Missing Data 
Missing data will not be imputed. Data that are excluded from the descriptive or 
inferential analyses will be included in the subject data listings. This will include data 
from subjects not in the particular analysis population, measurements from unscheduled 
visits, or extra measurements that may arise from 2 or more analyses of the biofluid 
sample at the same time point. Details on the handling of missing data will be further 
described in the SAP. 
4.10 Data Quality Assurance 
Completed eCRFs are required for each subject randomly assigned to treatment. 
Electronic data entry will be accomplished through the ClinSpark® remote electronic data 
capture system, which allows for on-site data entry and data management. This system 
provides immediate, direct data transfer to the database, as well as immediate detection of 
discrepancies, enabling site coordinators to resolve and manage discrepancies in a timely 
manner. Each person involved with the study will have an individual identification code 
and password that allows for record traceability. Thus, the system, and subsequently any 
investigative reviews, can identify coordinators, investigators, and individuals who have 
entered or modified records. 
 
Furthermore, the investigator retains full responsibility for the accuracy and authenticity 
of all data entered into the electronic data capture system. The completed dataset and 
their associated files are the sole property of the sponsor and should not be made 
available in any form to third parties, except for appropriate governmental health or 
regulatory authorities, without written permission of the sponsor. 
4.11 Data Sharing 


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De-identified subject-level data may be released to other researchers (including through a 
data warehouse or as a part of a publication) to enable secondary research. Additional 
secondary research may also be performed by the sponsor. 
 
5. ETHICAL CONSIDERATIONS 
5.1 Ethical Conduct of the Study 
This study will be performed in accordance with the recommendations guiding 
physicians in biomedical research involving human subjects adopted by the 18th World 
Medical Association General Assembly, Helsinki, Finland, 1964 and later revisions, as 
well as, United States Title 45 Code of Federal Regulations (CFR) Part 46 GCP, and 
International Council for Harmonisation (ICH) guidelines describing technical 
requirements for registration of pharmaceuticals for human use. 
5.2 Institutional Review Board (IRB) 
The FDA Project Lead or investigator will provide the designated IRB with all required 
documents, including the study protocol and informed consent form. The study will not 
be initiated until appropriate IRB approval is obtained from the designated IRB. The 
investigator will provide the FDA Project Lead with copies of the approval documents 
for the protocol, informed consent form, and all recruiting materials. The designated IRB 
will also receive copies of any original or amended information sheets or pamphlets 
given to the study subject in support of the informed consent process and any 
advertisements or other recruitment material. Such materials will not be employed in the 
study before approval by the designated IRB. 
 
Subjects will be informed that they have the right to contact the IRB or Office for Human 
Research Protections if they have any questions, concerns, complaints, or believe they 
have been harmed by the participation in this research study as a result of investigator 
negligence. Subjects will be given the address and phone number of the IRB. 
6. ADMINISTRATIVE PROCEDURES 
6.1 Responsibilities of the Investigator  
The following administrative items are meant to guide the investigator in the conduct of 
the study but may be subject to change based on industry and government standard 
operating procedures, working practice documents, or guidelines. Changes may be 
reported to the IRB but will not result in protocol amendments. 
6.1.1 Form FDA 1572 


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The investigator will complete and sign the Form FDA 1572. 
6.1.2 Adherence to Protocol  
The investigator agrees to conduct the study as outlined in this protocol in accordance 
with the ICH E6(R2) and all applicable guidelines and regulations. 
6.1.3 Reporting Requirements 
 
By participating in this study, the investigator agrees to submit reports of SAEs according 
to the timeline and method outlined in the protocol (Section 4.7.3.1.2). In addition, the 
investigator agrees to submit reports to the IRB as appropriate. The investigator also 
agrees to provide the sponsor with an adequate report shortly after completion of the 
investigator’s participation in the study. 
6.1.4 Source Documentation  
By participating in this study, the investigator agrees to maintain adequate case histories 
for the subjects treated as part of the research under this protocol. The investigator agrees 
to maintain accurate eCRFs and source documentation as part of the case histories. 
6.1.5 Retention of Records  
The investigator agrees to keep the records stipulated in this protocol and those 
documents that include (but are not limited to) the study-specific documents, 
identification log of all participating subjects, medical records, source worksheets, all 
original signed and dated informed consent forms, subject authorization forms regarding 
the use of personal health information (if separate from the informed consent form), 
copies of all eCRFs, query responses, and detailed records of drug disposition, to enable 
evaluations or audits from regulatory authorities, the sponsor, or its designees. 
Furthermore, ICH 4.9.5 requires the investigator to retain essential documents specified 
in Section 8 of ICH E6(R2) until at least 2 years after the last approval of a marketing 
application for a specified drug indication being investigated or, if an application is not 
approved, until at least 2 years after the investigation is discontinued and regulatory 
authorities are notified. In addition, ICH 4.9.5 states that the study records should be 
retained until an amount of time specified by applicable regulatory requirements or for a 
time specified in the clinical study site agreement between the investigator and sponsor. 
Refer to the clinical study site agreement for the sponsor’s requirements on record 
retention. The investigator should contact and receive written approval from the sponsor 
before disposing of any such documents. 
6.1.6 Financial Disclosure and Obligations 


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The investigator is required to provide financial disclosure information to allow the 
sponsor to submit the complete and accurate certification or disclosure statements 
required under 45 CFR 46. In addition, the investigator must provide to the sponsor a 
commitment to update this information promptly if any relevant changes occur during the 
course of the investigation and for 1 year after the completion of the study. 
Neither the sponsor nor the study clinic is financially responsible for further testing or 
treatment of any medical condition that may be detected during the screening process. 
6.2 Confidentiality and Disclosure of Data 
All subjects will sign a HIPAA-compliant authorization form containing the mandated 
core elements and requirements before participation in this clinical study. The sponsor 
and designees affirm and uphold the principle of the subject’s right to protection against 
invasion of privacy. Throughout this study, a subject’s source data will only be linked to 
the sponsor’s electronic data capture system database or documentation via a unique 
identification number. As permitted by all applicable laws and regulations, limited 
subject attributes such as gender, age or date of birth, and subject initials may be used to 
verify the subject and accuracy of the subject’s unique identification number. 
To comply with ICH Guidelines for GCP and to verify compliance with this protocol, the 
sponsor requires that the investigator allow review of the subject’s original medical 
records (source data or documents) by the study monitor, representatives from any 
regulatory authority (e.g., FDA), the sponsor’s designated auditors, and the appropriate 
IRB. These medical records will include, but will not be limited to, clinical laboratory 
test result reports, ECG reports, admission and discharge summaries for hospital 
admissions occurring during a subject’s study participation, and autopsy reports. Access 
to a subject’s original medical records requires the specific authorization of the subject as 
part of the informed consent process. 
Copies of any subject source documents that are provided to the sponsor must have 
personally identifiable information removed (i.e., subject name, address, and other 
identifier fields not collected in the subject’s eCRF). 
Data will be maintained and backed up in the electronic data capture system. All access 
to the data is protected by username and password, and each staff member and all sponsor 
staff will have separate access that requires a separate username and password. Access is 
only given to site staff and requested sponsor staff who have completed the appropriate 
training. 
6.3 Subject Consent 
Written informed consent in compliance with 45 CFR 46 will be obtained from each 
subject before entering the study or performing any unusual or nonroutine procedure that 


U.S. FOOD AND DRUG ADMINISTRATION  
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Pharmacology / Division Applied Regulatory Science 
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involves risk to the subject. An informed consent template may be provided by the 
sponsor to the study clinic. If any institution-specific modifications to study-related 
procedures are proposed or made by the study clinic, the consent should be reviewed by 
the sponsor or its designee or both before IRB submission. Once reviewed, the consent 
will be submitted by the investigator to the IRB for review and approval before the start 
of the study. If the informed consent form is revised during the course of the study, all 
active participating subjects must sign the revised form. 
Before enrollment, each prospective subject will be given a full explanation of the study 
and be allowed to read the approved informed consent form. The informed consent 
process will be performed by a clinical research nurse in a private room. The subject will 
be given unlimited time to ask questions regarding study participation, and each subject 
will be questioned to ensure their understanding. Once the investigator is assured that the 
subject understands the implications of participating in the study, the subject will be 
asked to give consent to participate in the study by signing the informed consent form. 
The investigator will provide a copy of the signed informed consent form to the subject. 
The original form will be maintained in the subject’s medical records at the site. 
6.4 Data Collection 
Full details of procedures for data collection and handling will be documented in the data 
management plan, which is initiated with the final protocol receipt. The data management 
plan is a changing document that evolves over the course of the study and is finalized by 
database lock. 
6.5 Publications 
No information related to or generated by this study will be released to the public until it 
has been reviewed by the sponsor. The sponsor shall own intellectual rights for the data 
and analysis resulting from this study. Authorship on publications will be determined by 
standard journal requirements. 
 
7. STUDY MANAGEMENT 
7.1 Monitoring 
The sponsor or its designee will monitor the study to ensure that it is being conducted 
according to the protocol, GCP standards, and applicable region-specific requirements, 
and to ensure that study initiation, conduct, and closure are adequate. The investigators 
and the study clinic staff will be expected to cooperate fully with the study monitors and 
personnel or agents of the sponsor and be available during monitoring visits to answer 


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questions sufficiently and to provide any missing information. The investigators and their 
institutions will permit direct access to source data/documents for study-related 
monitoring activities, audits, IRB reviews, and regulatory inspections. 
During any on-site visits, the study monitor will:  
x Check and assess the progress of the study 
x Review all informed consent forms 
x Review study data collected 
x Conduct source document verification 
x Identify any issues and address their resolution 
x Verify that the facility remains acceptable 
x Conduct study drug accountability 
These monitoring activities will be done in order to verify that the:  
x Data are authentic, accurate, and complete. 
x The safety and rights of the subjects are being protected. 
x The study is being conducted in accordance with the currently approved protocol 
(including any amendments), GCP, and all applicable regulatory requirements. 
In addition, the sponsor, designated auditors, and government inspectors must be allowed 
access to eCRFs, source documents, and other study files that may be required to evaluate 
the conduct of the study. 
7.2 Management of Protocol Amendments and Deviations 
7.2.1 Modification of the Protocol 
Any changes in this research activity, except those necessary to remove an apparent 
immediate hazard to the subject, must be submitted to the sponsor or designee and 
reviewed and approved by the local IRB before implementation. Amendments to the 
protocol must be submitted in writing to the investigator’s IRB for approval before 
subjects are enrolled into an amended protocol. 
7.2.2 Protocol Violations and Deviations 
Any significant protocol deviations that the investigator or study clinic staff believes are 
of major importance (e.g., incorrect randomizations, subject enrolled but not eligible) 


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should be reported to the sponsor and the investigator’s IRB as soon as possible. 
Significant protocol deviations may include the following: 
x Deviations from the inclusion/exclusion criteria that may affect subject safety 
x Deviations (omission or delay) of safety monitoring procedures 
x Deviations in the administration of the study drug 
x Deviations in obtaining informed consent 
All subjects who are enrolled and receive the study drug, regardless of whether they have 
a major protocol violation, must continue to be followed for safety for all follow-up study 
visits. 
 
 
 


U.S. FOOD AND DRUG ADMINISTRATION  
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Pharmacology / Division Applied Regulatory Science 
Protocol Number: SCR-012 
(Version 1.1) 
 
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U.S. FOOD AND DRUG ADMINISTRATION  
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U.S. FOOD AND DRUG ADMINISTRATION  
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37. Bertani A, Perna G, Arancio C, Caldirola D, Bellodi L. (1997).  Pharmacologic effect 
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44. Annerbrink K, Olsson M, Hedner J, Eriksson E. (2010). Acute and chronic treatment 
with serotonin reuptake inhibitors exert opposite effects on respiration in rats: 
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45. Nutt DJ, Forshall S, Bell C, Rich A, Sandford J, Nash J, Argyropoulos S. (1999). 
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46. Czachura JF, Rasmussen K. (2000). Effects of acute and chronic administration of 
fluoxetine on the activity of serotonergic neurons in the dorsal raphe nucleus of the 
rat. Naunyn Schmiedebergs Arch Pharmacol. 362(3):266-275 
 


U.S. FOOD AND DRUG ADMINISTRATION  
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Pharmacology / Division Applied Regulatory Science 
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47. Casey K, Duffin J, McAvoy GV. (1987). The effect of exercise on the central-
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0e84cc669388   
 
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cfe14e3a7e7e  
 
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56. Zofran Package Insert obtained from DailyMed dated 10/2017. Found at 
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57. Heydorn W.E (1999). Paroxetine: A review of its pharmacology, pharmacokinetics, 
and utility in the treatment of variety of psychiatric disorders. Expert Opin Investig 
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https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8cc25cf1-008c-4808-
baec-49f35a887fae  


U.S. FOOD AND DRUG ADMINISTRATION  
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Pharmacology / Division Applied Regulatory Science 
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59. Ondansetron Package Insert obstained from DailyMed dates 10/15/2021. Found at 
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8be2-eda701b51079  
 
60. Johannesen, L., Vicente, J., Mason, J. W., Sanabria, C., Waite-Labott, K., Hongm M., 
Strauss, D. G. (2014) Differentiating drug-induced multichannel black on the 
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verapamil. Clinical Pharmacology & Therapeutics, 96(5), 549-558. 
 
61. Garnett C, Bonate PL, Dang Q, Ferber G, Huang D, Liu J, Mehrotra D, Riley S, Sager 
P, Tornoe C, Wang Y (2018). Scientific white paper on concentration-QTc modeling. 
J Pharmacokinet Pharmacodyn, 45(3):383-397. 
 
62. E14/S7B Questions and Answers: Clinical and nonclinical evaluation of QT/QTc 
Interval Prolongation and Proarrhythmic Potential. Found at 
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U.S. FOOD AND DRUG ADMINISTRATION  
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Protocol Number: SCR-012 
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8. APPENDICES 
Appendix A – Schedule of Events 
 


U.S. FOOD AND DRUG ADMINISTRATION  
CDER / Office of Translational Sciences / Office of Clinical 
Pharmacology / Division Applied Regulatory Science 
Protocol Number: SCR-012 
(Version 1.1) 
 
 
Appendix B – List of Abbreviations 
LIST OF ABBREVIATIONS 
Abbreviation 
Definition 
AE 
adverse event 
Ag/Ab 
antigen/antibody 
AUC 
area under the concentration-time curve  
CDC 
Center for Disease Control 
CFR 
Code of Federal Regulations 
CI 
confidence interval 
Cmax 
maximum observed concentration 
COVID-19 
coronavirus disease of 2019 
CO2 
carbon dioxide 
CV 
coefficient of variation 
CYP 
cytochrome P450 
ECG 
electrocardiogram 
eCRF 
electronic case report form 
FDA 
Food and Drug Administration 
FSH 
follicle stimulating hormone 
GCP 
Good Clinical Practice 
HBsAg 
hepatitis B surface antigen 
HepC 
hepatitis C  
HIPAA 
Health Insurance Portability and Accountability Act 
HIV 
human immunodeficiency virus 
ICH 
International Council for Harmonisation 
IR 
immediate release 
IRB 
Institutional Review Board 
IV 
intravenous 
J-Tpeak 
early repolarization interval 
J-TpeakC 
heart rate-corrected J-Tpeak interval 
ǻ--TpeakC 
change-from-baseline in J-TpeakC 
ǻǻ--TpeakC 
placebo-adjusted change-from-baseline J-TpeakC 
Kel 
elimination rate 
Kg 
kilogram 
MedDRA 
Medical Dictionary for Regulatory Activities 
Mg 
milligram 
NONMEM 
nonlinear mixed effects modeling 
NSAID 
nonsteroidal anti-inflammatory drug 
N2 
nitrogen 
OTC 
over-the-counter 
O2 
Oxygen 


U.S. FOOD AND DRUG ADMINISTRATION  
CDER / Office of Translational Sciences / Office of Clinical 
Pharmacology / Division Applied Regulatory Science 
Protocol Number: SCR-012 
(Version 1.1) 
 
 
pCO2 
partial pressure carbon dioxide 
PD 
pharmacodynamic 
PETCO2 
end-tidal partial pressure carbon dioxide 
PK 
pharmacokinetic 
pO2 
partial pressure oxygen 
QA 
quality assurance 
QD 
once daily 
QTc 
heart rate-corrected QT interval 
ǻ47F 
change-from-baseline in QTc 
ǻǻ47F 
placebo-adjusted change-from-baseline QTc 
QTcF 
heart rate-corrected QT interval using the Fridericia 
correction 
RCF 
relative centrifugal force 
SAE 
serious adverse event 
SARS-CoV-2 
severe acute respiratory syndrome coronavirus 2 
SAP 
statistical analysis plan 
SD 
standard deviation 
SOP 
standard operating procedure 
SpO2 
oxygen saturation 
t1/2 
terminal half-life 
TEAE 
treatment-emergent adverse event 
Tmax 
time of Cmax 
VE55 
minute ventilation at 55 mmHg partial pressure carbon 
dioxide 
 
 
 
 


U.S. FOOD AND DRUG ADMINISTRATION  
CDER / Office of Translational Sciences / Office of Clinical 
Pharmacology / Division Applied Regulatory Science 
Protocol Number: SCR-012 
(Version 1.1) 
 
 
Appendix C – Protocol Revision History 
PROTOCOL REVISION HISTORY 
 
 
 
 
 
 
 
 
 
 
 
 
Protocol 
Number 
Version 
Effective Date 
Summary of Changes 
SCR-012 
1 
21 June 2022 
Developed initial protocol  
SCR-012 
1.1 
21 July 2022 
Updated protocol to reflect revised 
endpoints, assessments, and analyses 
method.  


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SAP_001.pdf: 
Study Title: Clinical Study to investigate the effect of administration of selective 
serotonin reuptake inhibitors and an opioid on ventilation 
 
Document Title: Statistical Analysis Plan – Study No. SCR-012 
 
Document Date: 1 September 2022 
 
NCT Number: NCT05470465 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 1 of 25 
 
 
Statistical Analysis Plan  
 
 
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Sponsor: 
U.S. Food and Drug Administration 
White Oak Building #64, Room 2072 
10903 New Hampshire Avenue 
Silver Spring, MD 20993 
 
Sponsor Study Lead: 
David Strauss, MD, PhD 
Director, Division of Applied Regulatory Science  
U.S. Food and Drug Administration 
Telephone: 301-796-6323 
Email: david.strauss@fda.hhs.gov 
 
Sponsor Medical 
Monitor: 
Keith Burkhart, MD 
U.S. Food and Drug Administration 
Telephone: 301-796-2226 
Email: keith.burkhart@fda.hhs.gov 
 
Project Manager: 
Jeffry Florian, PhD 
U.S. Food and Drug Administration  
Telephone: 301-796-4847 
Email: jeffry.florian @fda.hhs.gov 
Version of SAP: 
1.0 
 
Date of SAP: 
1 September 2022 
 
CONFIDENTIAL 
 
The concepts and information contained in this document or generated during the study are 
considered proprietary and may not be disclosed in whole or in part without the expressed 
written consent of the U.S. Food and Drug Administration. 
 
 
 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 2 of 25 
 
 
 
Sponsor Signatures Page 
 
Prepared by 
 
 
 
 
 
Victoria Gershuny, PhD 
Biologist 
Division of Applied Regulatory Science  
U.S. Food and Drug Administration 
 
Date 
Prepared by 
 
 
 
 
 
Pablo Salcedo, MD 
Pharmacokineticist 
Division of Applied Regulatory Science  
U.S. Food and Drug Administration 
 
Date 
 
 
 
 
Approved by 
Jeffry Florian, PhD 
Associate Director 
Division of Applied Regulatory Science 
U.S. Food and Drug Administration 
 
Date 
 
 
Pablo Salcedo -S
Digitally signed by Pablo Salcedo -S 
Date: 2022.09.01 17:01:30 -04'00'
Victoria Gershuny -S 
(Affiliate)
Digitally signed by Victoria 
Gershuny -S (Affiliate) 
Date: 2022.09.01 17:03:48 -04'00'
Jeffry Florian -S
Digitally signed by Jeffry Florian -S 
Date: 2022.09.01 17:08:14 -04'00'


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 3 of 25 
 
 
Contents 
Sponsor Signatures Page .......................................................................................................... 2 
Contents .................................................................................................................................. 3 
1. 
Introduction...................................................................................................................... 6 
2. 
Study Objectives .............................................................................................................. 6 
2.1 
Primary Objective ...................................................................................................... 6 
2.2 
Secondary Objectives................................................................................................. 6 
2.3 
Exploratory Objectives .............................................................................................. 6 
3. 
Study Endpoints ............................................................................................................... 6 
3.1 
Primary Endpoints ..................................................................................................... 6 
3.2 
Secondary Endpoints ................................................................................................. 6 
3.3 
Exploratory Endpoints ............................................................................................... 7 
4. 
Study Overview................................................................................................................ 8 
4.1 
Study Design ............................................................................................................. 8 
4.2 
Sample Size............................................................................................................... 9 
5. 
Analysis Populations ........................................................................................................ 9 
6. 
Data Screening and Acceptance ...................................................................................... 10 
6.1 
Handling of Missing or Incomplete Data .................................................................. 10 
7. 
General Statistical Considerations ................................................................................... 11 
7.1 
Subject Disposition .................................................................................................. 11 
7.2 
Demographic and Baseline Characteristics................................................................ 11 
7.3 
Pharmacodynamic Analyses ..................................................................................... 11 
7.3.1 
Rebreathing Analyses ....................................................................................... 11 
7.3.2 
Exploratory Ventilation Measures ..................................................................... 16 
7.3.3 
Electrocardiogram Analyses .............................................................................. 17 
7.3.4 
Pupillometry Analyses ...................................................................................... 18 
7.3.5 
Sedation Score Analyses ................................................................................... 18 
7.4 
Pharmacokinetic Analyses ....................................................................................... 19 
7.4.1 
Plasma Pharmacokinetics .................................................................................. 19 
7.4.2 
PK/PD Analyses ............................................................................................... 20 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 4 of 25 
 
 
7.5 
Safety Analyses ....................................................................................................... 20 
7.5.1 
Adverse Events................................................................................................. 20 
7.5.2 
Clinical Laboratory Tests .................................................................................. 20 
7.5.3 
Vital Sign Measurements .................................................................................. 21 
7.5.4 
Safety 12-lead Electrocardiograms .................................................................... 21 
7.5.5 
Pulse Oximetry and Telemetry .......................................................................... 21 
7.5.6 
Physical Examinations ...................................................................................... 21 
7.5.7 
Other Safety Data ............................................................................................. 21 
8. 
Data Quality Assurance .................................................................................................. 21 
9. 
Appendices .................................................................................................................... 23 
9.1 
Randomization Schedule .......................................................................................... 23 
9.2 
Nonlinear Regression Model .................................................................................... 24 
10. References ..................................................................................................................... 25 
 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 5 of 25 
 
 
Table of Abbreviation 
Abbreviation 
Definition 
AE 
adverse event 
AUC 
area under the concentration-time curve  
CI 
confidence interval 
CV 
coefficient of variation  
Cmax 
maximum observed concentration 
ECG 
electrocardiogram 
eCRFs 
electronic case report forms 
FDA 
Food and Drug Administration 
IV 
intravenous 
Kel 
elimination rate 
J-Tpeak 
early repolarization interval 
O2 
oxygen 
pCO2 
partial pressure of carbon dioxide  
PD 
pharmacodynamic 
PETCO2 
end-tidal pCO2 
PK 
pharmacokinetic 
pO2 
partial pressure oxygen 
QTc 
heart rate-corrected QT interval 
ǻ47F 
change-from-baseline in QTc 
ǻǻ47F 
placebo adjusted change from baseline QTc 
QTcF 
heart rate-corrected QT interval using the Fridericia correction 
SD 
standard deviation 
SOP 
standard operating procedures 
TEAE 
treatment-emergent adverse event 
Tmax 
time of maximum concentration (Cmax) 
t1/2 
terminal half-life 
VE55 
minute ventilation at 55 mm Hg PETCO2 
ǻ9( 
baseline-adjusted VE55 
VRT 
Ventilatory recruitment threshold 
 
   
 
 
 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 6 of 25 
 
 
1. Introduction 
This document outlines the proposed statistical methods for data analysis of data collection from 
Protocol ‘SCR-012 Clinical study to investigate the effect of administration of selective 
serotonin reuptake inhibitors and an opioid on ventilation.  
2. Study Objectives 
2.1 Primary Objective 
The two separate primary objectives include the following: 
x To study ventilatory effects of selective serotonin reuptake inhibitors (SSRIs) (paroxetine 
or escitalopram) combined with oxycodone compared to oxycodone alone after 21 days 
of SSRI dosing. 
x To study ventilatory effects of SSRIs (paroxetine or escitalopram) compared to placebo 
after 20 days of SSRI dosing.   
2.2 Secondary Objectives 
Secondary objectives include the following: 
x To study ventilatory effects of SSRIs (paroxetine or escitalopram) combined with 
oxycodone compared to oxycodone alone after 6 and 12 days of SSRI dosing. 
x To study  ventilatory effects of SSRIs (paroxetine or escitalopram) compared to placebo 
after 5 and 11 days of SSRI dosing. 
2.3 Exploratory Objectives 
Exploratory objectives include the following: 
x To study whether paroxetine or escitalopram affects the pharmacokinetics of oxycodone. 
x To evaluate differences in hypercapnic ventilatory response under hyperoxic or hypoxic 
rebreathing. 
x To study whether there is a direct pharmacodynamic interaction between paroxetine or 
escitalopram and oxycodone. 
x To summarize additional pharmacokinetic parameters and pharmacodynamic 
measurements collected during the study. 
3. Study Endpoints 
3.1 Primary Endpoints 
The following primary endpoints will be evaluated: 
x Minute ventilation at 55mm Hg end tidal CO2 (VE55) under hyperoxic conditions on day 
21 
x VE55 under hyperoxic conditions on day 20  
3.2 Secondary Endpoints 
The following secondary endpoints will be evaluated: 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 7 of 25 
 
 
x VE55 under hyperoxic conditions on days 6 and 12 
x VE55 under hyperoxic conditions on days 5 and 11 
3.3 Exploratory Endpoints 
The following exploratory PK parameters will be determined for oxycodone and oxymorphone 
(days 6, 12, and 21) and paroxetine, escitalopram, and escitalopram metabolites (days 2, 5, 6, 11, 
12, 16, 20, and 21): 
x Maximum observed plasma concentration (Cmax) 
x Area under the plasma concentration time curve (AUC) 
x Time at which Cmax occurs (Tmax) 
x Elimination rate constant (Kel) 
x Terminal half-life (t1/2) 
x Accumulation ratio (for escitalopram and paroxetine) 
Additionally, the following exploratory PD markers may be evaluated:  
Ventilation and Cardiovascular Assessments:  
x During rebreathing stage 
o VE55 (minute ventilation at the 55mm Hg end tidal CO2 point) 
o Baseline minute ventilation when end tidal PCO2 is less than the ventilatory 
recruitment threshold (represents non-chemoreflex drives to breathe) 
o Ventilatory recruitment threshold (end tidal PCO2 above which minute ventilation 
starts to increase linearly with further increases in end tidal PCO2) 
o Slope of the minute ventilation / end-tidal partial pressure of carbon dioxide (end-
tidal PCO2) regression line that reflects the increase in minute ventilation relative 
to the increase in end tidal PCO2 (represents chemoreflex sensitivity) 
o Extrapolated ventilation recruitment threshold (intersection with x axis) 
x During relaxation stage 
o Minute ventilation, tidal volume, respiratory rate, end-tidal PCO2, end-tidal PO2, 
oxygen saturation, and heart rate during the relaxation stage 
o Number of apneic events lasting > 10 s during the relaxation stage 
Pupillary Assessments  
x Maximum pupil diameter before constriction  
x Minimum diameter at peak constriction  
x Percent change between min/max diameter  
x Latency of constriction   
x Average constriction velocity  
x Maximum constriction velocity  
x Dilation velocity after peak constriction  
x Time to reach 75% recovery of maximum diameter  
Sedation scores   
x Ramsey Sedation Scale   
x Visual Analogue Scale   


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 8 of 25 
 
 
ECG Assessments  
x Change from baseline in QTc, PR, QRS, J-TpeakC, Tpeak-Tend and heart rate. 
An exploratory endpoint is the pharmacokinetic/pharmacodynamic (PK/PD) relationship for 
study drugs when administered alone versus in combination. 
4. Study Overview 
4.1 Study Design 
This study will be a randomized, double blind, three period crossover study with approximately 
25 healthy volunteer participants. This study will include three 21-day treatment periods with a 
3-week washout between each period. Each subject will be randomized to 1 of 6 treatment 
sequences (i.e., ABC, ACB, BAC, BCA, CAB, CBA). FDA will prepare the randomization 
schedule. 
 
Participants will enter the clinic on a staggered basis in cohorts of approximately five so that no 
more than five subjects are undergoing rebreathing on any given day. Subjects will be staggered 
to allow for direct safety overview by medical staff during Duffin Rebreathing procedure.  
Participants will receive either placebo, paroxetine, or escitalopram on days 1-21 for each period 
(see below table). Oxycodone will be administered on days 6, 12, and 21 of each period. Dosing 
of the study drugs will occur at time 0 on each day. Oxycodone dosing will occur at 3 h so that 
maximum concentration occurs  at approximately the same time for all drugs. Participants will 
also receive ondansetron 4 mg 30 min before oxycodone administration.  
Participants will be confined to the study clinic from Day -1 the morning of Day 22 for each 
period. There will be a three-week washout between each period. Subjects will be discharged 
from the study after completion of all study procedures. If a subject discontinues from the study 
prematurely, all procedures scheduled for the end of the study will be performed. Meal timing 
and components, activity levels, and general conditions in the study clinic will be as similar as 
possible on the treatment days. 
Upon return to clinic, on Days 42 & 84, eligibility criteria to continue study participation will be 
reviewed (see Schedule of Events for criteria listed on Days 42 & 84), any changes in medical 
history (including concomitant medications) will be documented. 
Day -1 
Days  
1-21 
Day  
22 
Days  
23-41 
Day  
42 
Days  
43-63 
Day  
64 
Days  
64-83 
Day  
84 
Days  
85-105 
Day  
106 
Check-in  
1 
Period  
1 
Check-out  
1 
Washout  
1 
Check-in  
2 
Period  
2 
Check-out  
2 
Washout  
2 
Check-in  
3 
Period  
3 
Check-out  
3 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 9 of 25 
 
 
 
4.2 Sample Size 
Approximately 25 healthy participants are planned for enrollment. The primary endpoint is a 
comparison of VE55 between two treatment on day 21 (oxycodone with the concomitant 
medication versus oxycodone alone) and on day 20 (concomitant medication versus placebo). 
The comparisons for day 20 and 21 will be considered as separate primary endpoints, each tested 
at a 0.025 significance level.  
A previous study (20 participants) with paroxetine showed a decrease in 10.2 L/min in VE55 for 
paroxetine (40 mg) combined with oxycodone (10 mg) compared to oxycodone alone after 5 
days of dosing with paroxetine (NCT04310579). Similarly, there was a 9.3 L/min decrease in 
paroxetine compared to placebo after 4 days of dosing with paroxetine. The standard deviation in 
assessments was approximately 6.5 L/min. Assuming a similar effect size with paroxetine and 
escitalopram at day 20 and 21, the planned number of participants allows for a 40% drop out rate 
while maintaining at least 90% power for separate one-sided tests at a 0.025 significance level 
with the multiple primary endpoints. Study sample size did not consider secondary endpoints. 
5. Analysis Populations 
The rebreathing analysis population will include all subjects who completed at least one 
rebreathing assessment on any day or at any timepoint.   
For calculating the primary endpoint, the rebreathing analysis population will be subset to those 
subjects with data from at least two treatments and rebreathing assessments at the primary PD 
endpoint timepoint (5 h on day 20 and day 21, respectively).  A subject who discontinues dosing 
after the primary timepoint on day 20 but before the primary timepoint on day 21, would still be 
part of the analysis population for the primary endpoint on day 20 but not for day 21.  
Subjects in the rebreathing analysis population will be used for the planned primary, secondary, 
and exploratory analyses related to evaluating drugs effects on ventilation.  If a subject does not 
contribute data from all treatments due to early discontinuations or other reasons, only those 
comparisons where the subject has all required data will be performed.  
 
Treatment 
Day 
1-5 
6 
7-11 
12 
13-20 
21 
A 
Placebo 
Placebo +  
10 mg oxycodone 
Placebo 
Placebo +  
10 mg oxycodone 
Placebo 
Placebo + 
10 mg oxycodone 
B 
40 mg 
paroxetine  
40 mg paroxetine 
+ 10 mg 
oxycodone 
60 mg paroxetine 60 mg paroxetine 
+ 10 mg 
oxycodone 
60 mg paroxetine 
60 mg paroxetine 
+ 10 mg 
oxycodone 
C 
20 mg 
escitalopram 
20 mg 
escitalopram +  
10 mg oxycodone 
30 mg 
escitalopram 
30 mg 
escitalopram +  
10 mg oxycodone 
30 mg 
escitalopram 
30 mg 
escitalopram + 10 
mg oxycodone 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 10 of 25 
 
 
A rebreathing assessment will be considered complete if the subject makes it through the entire 
procedure (e.g., subject makes it to the rebreathing stage with sufficient data collected to 
estimate VE55) and if there are no identifiable issues with how the procedure was conducted.  
Potential issues with how the procedure was conducted can include, but are not limited to, a leak 
from the system (e.g., substantially decreasing O2 during rebreathing or no evidence of an 
increase in CO2 during rebreathing), inaccurate readings from the pneumotach (e.g., non-
physiologic baseline minute ventilation readings), or a subject suddenly increasing minute 
ventilation without subsequent increases in minute ventilation as end tidal pCO2 increases 
(suggesting stress-associated or other non-CO2 mediated hyperventilation confounding the 
ventilatory response to hypercapnia through [H+] chemoreceptors). Determination of the 
completeness of each rebreathing assessment and its individual components/measurements will 
be performed manually by two members blinded from treatment information (see Section 7.3).   
The PK population will include all subjects who receive study drug and have at least 1 estimable 
PK parameter after dosing. 
The ECG exposure-response population will include all subjects who receive at least 1 dose of 
any of the study drugs and have digital ECG (QTc and J-TpeakC) data for the treatment period 
collected before dosing and at 1 or more time points after dosing as well as plasma concentration 
data (except for the placebo arm) from the same time points after dosing. Subjects in this 
population will be used for the ECG exposure-response analysis. 
The safety population will include all subjects who receive at least 1 dose of any of the study 
drugs. 
6. Data Screening and Acceptance 
6.1 Handling of Missing or Incomplete Data  
The following will be performed: 
x PK measurements below the quantification limits will be considered equal to zero for all 
analyses.  
x Missing PK or PD data (e.g., subject discontinued from study; subject could not 
successfully complete rebreathing at a time point) will not be imputed. Data that are 
excluded from the descriptive or inferential analyses will be included in the subject data 
listings.   
x Pupillometry data collected from the PLR®-3000 pupillometer device flagged as being 
anomalous based on device error codes will be excluded from analyses. 


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7. General Statistical Considerations 
All data will be presented in data listings. Data from subjects excluded from an analysis 
population will be presented in the data listings, but not included in the calculation of summary 
statistics. 
7.1 Subject Disposition 
The number of subjects who enroll in the study and the number and percentage of subjects who 
complete each assessment by study part will be presented. The frequency and percentage of 
subjects who withdraw or discontinue from the study and the reason for withdrawal or 
discontinuation will be summarized. 
7.2 Demographic and Baseline Characteristics 
Continuous demographic and baseline characteristic variables (e.g., age, height, weight, and 
body mass index) will be summarized by study part and by treatment using descriptive statistics 
(number of subjects, mean, SD, median, minimum, maximum, and interquartile range). The 
number and percentage of subjects in each class of categorical demographic and baseline 
characteristic variables will also be summarized.  
7.3 Pharmacodynamic Analyses 
7.3.1 Rebreathing Analyses 
Figure 7-1 below shows representative time-course results from the rebreathing procedure, with 
minute ventilation, oxygen percentage, and end-tidal PCO2 shown from top to bottom.  
Throughout the procedure subjects will undergo different steps designed to reduce noise and 
variability.   Initially, subjects breathe room air for 5 minutes and relax as much as possible. 
Around the 5-minute mark, the subject is instructed to begin hyperventilating (primarily through 
deep breathing) for 5 min to achieve an end tidal PCO2 of approximately 20-25 mmHg prior to 
rebreathing. During rebreathing procedures, subjects will be maintained at one of 2 different 
isoxic end tidal PO2. The isoxia at a hyperoxic (150 mmHg) or hypoxic (50 mmHg) end tidal 
PO2 will be maintained by providing a computer-controlled flow of 100% O2 to the rebreathing 
bag. The hyperoxic rebreathing procedures will be performed at 0, 4, and 5 h on days 5, 6, 11, 
12, 20, and 21. The hypoxic rebreathing procedure will be performed on the same days at 5 h 
immediately following the hyperoxic rebreathing assessment.     
Each of these steps can be noted on the example figure below (7-1).  In this example, relaxation 
while breathing room air was performed for 5-minutes.  From 5 to 10 minutes, the test subject 
began hyperventilation and slight decreases in O2% and PCO2 with an increase in minute 
ventilation are observed.  Finally, the test subject begins rebreathing at 10 minutes.  After taking 
deep breaths, PCO2 in the rebreathing circuit and the lungs equilibrate and then PCO2 increases 
linearly to approximately 55 mm Hg at the end of rebreathing in this subject.  An increase in 


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minute ventilation is triggered at a certain point during rebreathing (ventilatory recruitment 
threshold), and both measures increase until completion of the procedure based on subject 
tolerability or until other procedure stopping criteria are reached (see protocol and rebreathing 
SOP for full list). If the subject’s data does not follow these trends due to a leak in the apparatus 
(e.g., incomplete seal between the mask and subject’s face), inaccurate readings from the 
pneumotach, issues in operator recording of the data, or the subject not having a linear increase 
in minute ventilation as end tidal PCO2 increases prior to reaching PCO2 of 55 mm Hg, the run 
will not be considered completed and will be excluded from subsequent data analysis that is 
dependent on the minute ventilation/end tidal PCO2 regression line. 


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Figure 7-1: Sample data from a test subject during relaxation, hyperventilation, and 
rebreathing, with minute ventilation, O2 percentage, and PCO2 mmHg over time during these 
experimental steps. A representative hyperoxic test is shown at the top (oxygen percentage 
maintained at ~21% during rebreathing) and a representative hypoxic test is shown at the 
bottom (oxygen percentage maintained at ~7.1% during rebreathing). 
 
From these results, minute ventilation and end tidal PCO2 levels over time will be matched. End 
tidal PCO2 will be calculated as % CO2 • (barometric pressure – 47 mmHg [water vapor]). 
Separate piecewise linear and nonlinear (hockey stick model) regressions will be fit to the 
experiment data. The nonlinear and piecewise linear regressions will be fit to data from the 
rebreathing stage of the rebreathing procedure (i.e., during isoxic hypercapnia).  This functional 
relationship for the nonlinear model assumes a constant relationship between minute ventilation 
and end tidal PCO2 up until a threshold value is reached, after which minute ventilation and end 
tidal PCO2 both increase linearly.  Example code for the nonlinear fit can be found in the 
Appendix, and a sample result from the test case can be seen in Figure 7-2.  Because of potential 
inconsistencies in when the stage transition may have been flagged by the device operator 
(pressed while hyperventilation was still ongoing) and as the isoxic setpoint is being achieved, 
the first 15 to 30 seconds of data from the rebreathing stage (based on visual inspection) will be 
removed when calculating the regressions. In addition, all other exploratory pharmacodynamic 
endpoints will be automatically calculated. 
 
Because of the potential for outlying data points in the minute ventilation and/or end-tidal PCO2 
signal at each individual breath, it is sometimes necessary to exclude outlying data points from 
the regression. Such outlying data points can be introduced by subject postural changes, sighing, 
hiccups, talking, or faulty sensors. In addition, there may be a need to remove additional data at 
the beginning of rebreathing or to remove data at the end of rebreathing (e.g., nonlinearity as 
subject approaches or exceeds end tidal PCO2 55 mmHg).  
Outlying values for the regressions will be identified automatically through evaluation of 
standardized residuals after performing the initial regression (i.e., standardized residuals > 2).  
Then, the data analysis team will be provided with time course plots from the full assessment (all 
rebreathing procedure stages with stage transitions marked) and regression results using data 
from the rebreathing stage. The data analysis team will evaluate the completeness of the 
rebreathing assessment and visually assess the automatically calculated values in comparison to 
the underlying data. Any automatically calculated values that do not accurately capture the 
underlying data will be flagged, additional outliers will be removed, and the automated 
calculations will be re-run. A subject may have incomplete rebreathing data not supporting 
calculation of one or more primary endpoints, but other endpoint measures will still be used for 
analyses. 


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If the nonlinear regression converges, the regression results will be used to derive ventilation for 
that subject at that assessment. Baseline minute ventilation when end tidal PCO2 is less than the 
ventilatory recruitment threshold is the V0 parameter from the regression. Likewise, the slope of 
the PCO2-ventilatory response curve is the sslope parameter from the regression. The ventilatory 
recruitment threshold is calculated as the intersection between the two line segments. The 
extrapolated ventilatory recruitment threshold is calculated as the intersection of the PCO2-
ventilatory response curve and the x-axis. If the nonlinear regression does not converge, results 
from the piecewise linear regression will be used to determine the slope of the PCO2-ventilatory 
response curve and data from the relaxation stage will be used to determine baseline minute 
ventilation. The ventilatory recruitment threshold and the intersection of the PCO2-ventilatory 
response curve and the x-axis will then be calculated as described above. All modeling analyses 
for the regressions will be performed in statistical software.
Figure 7-2: Sample nonlinear least squares fit between minute ventilation and end tidal PCO2
for test subject under hyperoxic (left) or hypoxic (right) conditions. Different hypercapnic 
ventilation endpoints of interest are annotated on each figure.
The estimated VE55 from the regression will be used for primary endpoint analyses. All 
modeling analyses for the regressions will be performed in statistical software. This model will 
be used to predict minute ventilation at pCO2 of 55 mmHg (i.e. VE55). If a subject does not 
reach 55 mmHg, the model will be extrapolated to predict the on-treatment minute ventilation at 
55 mmHg.  Baseline-adjusted VE55 (ǻVE55) will be calculated for each subject at each time 


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point by subtracting on-treatment VE55 from baseline (i.e., hyperoxic and hypoxic rebreathing 
assessments performed on day -1).  
7.3.1.1 Primary Analyses 
Minute ventilation and end-tidal pCO2 (PETCO2) data from the rebreathing stage of the Duffin 
Rebreathing procedure will be analyzed at the specified primary timepoints using nonlinear and 
piecewise linear regressions. The regressions will be used to predict VE55 as described in 
Section 7.3.1.  
Multiple primary analyses are planned for each drug. The first primary analysis will be VE55 on 
day 21 at 5 h (hyperoxic) between oxycodone with paroxetine or escitalopram compared to 
oxycodone alone. The second primary analysis will be VE55 on day 20 at 5 h (hyperoxic) between 
paroxetine or escitalopram compared to placebo. Since Day 20 and 21 are considered multiple 
primary endpoints, comparisons will have an adjustment for multiplicity using a Bonferroni 
correction (each day will be tested at a 0.025 significance level). No adjustments will be made for 
separate testing of paroxetine or escitalopram since the treatments are considered separate 
interventions in the study.  
A linear mixed effects model will be developed using all study data from hyperoxic assessments. 
Fixed effects will include treatment, period, sequence, and baseline VE55 (i.e., VE55 obtained at 
0 h on Day -1 of each treatment period).  Subject will be included as a random effect on the 
intercept.  If a subject’s baseline VE55 for a treatment period is not available, then the baseline 
value for that period will be calculated based on the median of all other baseline values for that 
subject from other study periods.  If a subject does not have any completed baseline VE55 data, 
the subject will be assigned a baseline VE55 equal to the median of the population.  
The Kenward-Roger approximation will be used to estimate denominator degrees of freedom for 
tests of fixed effects. Normality assumption will be verified using the Shapiro-Wilke test for 
normality. Homogeneity of variances will be verified using Levene’s test. If the data in its original 
or transformed form does not satisfy assumptions for normality and homogeneity, a Wilcoxon 
signed-rank test will be used for all comparisons rather than a linear mixed effect model. I 
To demonstrate an effect when an SSRI (paroxetine or escitalopram) is combined with oxycodone 
compared to oxycodone alone, the upper bound of the one-sided 97.5% CI of the least-square mean 
VE55 difference between treatments at day 21 must not overlap 0 L/min. Similarly, to demonstrate 
an effect of paroxetine (or escitalopram) compared to placebo, the upper bound of the one-sided 
97.5% CI of the least-square mean VE55 difference between treatments at day 20 must not overlap 
0 L/min. Each comparison will be performed separately (i.e.,þtrt’ asþparoxetine’ 
orþescitalopram’):  
Day 21: 
•H0: VE55oxy+trt - VE55oxy /PLQ 


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•HA: VE55oxy+trt - VE55oxy < 0 L/min 
Day 20: 
•H0: VE55trt - VE55placebo /PLQ 
•HA: VE55trt - VE55placebo < 0 L/min 
7.3.1.2 Secondary Analyses 
Two separate sets of secondary endpoints are planned for the study. Effects of SSRIs (paroxetine 
or escitalopram) with oxycodone compared to oxycodone alone will be performed on day 6 and 
day 12 at the 5 h (hyperoxic) timepoint. As additional secondary endpoints, effects of SSRIs 
(paroxetine or escitalopram) alone compared to placebo will be determined on day 5 and 11 at the 
5 h (hyperoxic) timepoint. The linear mixed effect model developed for the primary analyses will 
be used for these comparisons.  
Testing for the secondary endpoints will be performed in a hierarchical manner. If a significant 
difference is observed at day 21 between treatment combined with oxycodone compared with 
oxycodone alone, then comparisons between treatment combined with oxycodone compared with 
oxycodone alone will be performed at a 0.025 significance level for day 12. To demonstrate an 
effect when a treatment is combined with oxycodone compared to oxycodone alone, the upper 
bound of the one-sided 97.5% CI of the least-square mean VE55 difference between treatments at 
day 12 must not overlap 0 L/min. If a significant difference is observed for day 12, then similar 
testing will be performed at day 6. If either the original primary or first secondary comparison 
fails, then comparisons will still be performed and the one-sided 97.5% CI of the least-square mean 
VE55 difference between treatments will be reported without a p-value.  
A similar approach will be utilized for comparisons between treatments and placebo. If a 
significant difference is observed at day 20 between treatment compared with placebo, then 
comparisons testing will be performed at a 0.025 significance level for day 11. To demonstrate an 
effect with treatment compared to placebo, the upper bound of the one-sided 97.5% CI of the least-
square mean VE55 difference between treatments at day 11 must not overlap 0 L/min. If day 11 
passes, then similar testing will be performed at day 5. If either the original primary or first 
secondary comparison fails, then comparisons will still be performed and the one-sided 97.5% CI 
of the least-square mean VE55 difference between treatments will be reported without a p-value. 
7.3.2 Exploratory Ventilation Measures 
In addition to planned VE55 primary and secondary analyses, data will be summarized by 
treatment, treatment day, and time point using descriptive statistics (number of subjects, mean, 
SD, median, minimum, maximum, confidence intervals).  Both VE55 and ǻVE55 time course 
profiles will be calculated and plotted for the overall treatments and for individuals. Additional 
comparisons may be performed at other study time points to determine consistency of responses 
observed at the 5-h timepoint. Comparisons between hypercapnic ventilatory response measures 


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from hyperoxic or hypoxic rebreathing assessments at the 5-h timepoint will be performed using 
paired t-tests. These analyses will be considered hypothesis--generating and exploratory. 
Other exploratory respiratory measures will be calculated and summarized from information 
collected during planned rebreathing procedures (see Section 3.3).  Baseline minute ventilation, 
ventilatory recruitment threshold, slope of the PCO2-ventilatory response curve, and the 
extrapolated ventilatory recruitment threshold will be calculated for each subject at each 
rebreathing assessment. Data collected during the Duffin Rebreathing procedure will be used to 
determine the slope of the minute ventilation / PETCO2 regression line.  Resting ventilation, tidal 
volume, end-tidal PCO2, and oxygen saturation will be determined using data from the relaxation 
portion of the Duffin Rebreathing procedure.  All measures will be summarized by treatment, 
day, and time using descriptive statistics (number of subjects, mean, SD, median, minimum, and 
maximum, confidence intervals). Comparisons may be performed across treatment groups or by 
subgroups (e.g., demographic variables) to further explore treatment results. Time course profiles 
for all measures will be calculated and plotted.  Comparisons between hypercapnic ventilatory 
response measures from hyperoxic or hypoxic rebreathing assessments at the 5-h timepoint will 
be performed using paired t-tests. These analyses will be considered both -hypothesis generating 
and exploratory. 
Apneic events lasting > 10 s will be determined using data collected during relaxation and 
preparation portion of the Duffin Rebreathing procedure.  An event is defined as the absence of 
inspiratory flow (as measured by the pneumotachograph) for at least 10 s during this period.  
These parameters will be summarized using descriptive statistics (number of subjects, number of 
events) by study part, treatment, day, and time, as appropriate.  
7.3.3 Electrocardiogram Analyses 
The QT interval will be corrected for heart rate using Fridericia’s formula (QTc=QT/RR1/3). The 
J-Tpeak interval will be corrected for heart rate using the formula (J-TpeakC = J-TpeakC/RR0.58). 
Baseline will be the mean of the 3 predose ECG extractions of Day 1. 
Exposure-response analyses will be performed for the change-from-EDVHOLQHLQ47Fǻ47FDQG
change from baseline in other ECG measurements, where the mean of the 3 predose ECG 
readings on Day 1 will be used as the baseline. The concentration of the drug will be used as a 
covariate. Exposure-response analysis will be done following most recent best practices in 
concentration-QTc modeling.  
To assess the appropriateness of a linear model, normal QQ-plots for the weighted residuals 
versus concentration and weighted residuals versus fitted values will be produced. A model with 
a quadratic term in concentration will be fitted and the quadratic term will be tested on the 2-
sided 5% alpha level. In case of a significant quadratic term, nonlinear models, such as a 


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loglinear model and an Emax model, will be investigated and the primary model will be selected 
based on the Akaike Information Criterion and plausibility arguments.  
Unless the prespecified test procedure for linearity indicates otherwise, the ECG analysis will be 
based on a linear mixed effects model implemented in R softwareZLWKǻ47FDVWKHGHSHQGHQW
variable, drug plasma concentration and baseline QTc as continuous covariates, treatment and 
time point as categorical factors, and subject specific random effects for the intercept and slope. 
All postdose data will be used. The degrees of freedom for the model estimates will be 
determined by the Kenward-Rogers method. From the model, the slope (i.e., the regression 
parameter for the concentration) and the treatment effect will be estimated together with 2-sided 
90% CIs. 
The predicted mean placebo-adjusted change from baseline QTc (ǻǻQTc) at the observed 
geometric mean Cmax LHWKHSURGXFWZLWKWKHVORSHHVWLPDWHௗௗWUHDWPHQWHIIHFW>ǻQTcactive – 
ǻQTcplacebo]) and the 2--sided 90% CI of the estimate will be calculated for days 2 and 16.  
Exposure response analysis, similar to that described for QTc will be applied to JTpeakC, PR, 
QRS, and Tpeak-Tend for data from days 2 and 16. 
For each time point, an analysis of variance model will be fitted with ǻQTc as the dependent 
variable, treatment (active or placebo) as the factor, and baseline QTc as a covariate. From this 
model, the difference (ǻQTcactive – ǻQTcplacebo) will be estimated with a 2-sided 90% CI. 
Separate models will be fitted for each treatment, all of them using the same placebo data. 
Change from Baseline in heart rate, JTpeakC, PR, QRS, and TpeakTend will be calculated using 
descriptive summary statistics. 
7.3.4 Pupillometry Analyses 
Maximum pupil diameter before constriction and dynamic pupillary measurements after a light 
stimulus will be measured before and after each rebreathing assessment (except  in between the 
hyperoxic and hypoxic paired assessments). These exploratory parameters (see Section 3.3) will 
be summarized using descriptive statistics (number of subjects, mean, SD, median, minimum, 
maximum, confidence intervals). Time course summaries of each pupillary measurement will be 
generated for all treatment groups.  Pupillary changes will be compared to baseline 
measurements between treatments to evaluate the effect of different interventions on pupillary 
changes.  In addition, time course pupillary changes will be compared to time course ventilatory 
changes across treatments to evaluate concordance between these measures when subjects 
receive different drugs and drug combinations. 
7.3.5 Sedation Score Analyses 
The Ramsay Sedation Scale is an observer-based assessment of sedation, with a scale of 1-6, that 
will be collected for each subject  during the relaxation period of each Duffin Rebreathing 
procedure.  In addition, subjects will be asked to provide their own assessment using the Visual 


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Analog Scale for sedation (a perpendicular mark on a 100 mm line with a scale of 0 [‘awake and 
alert’] to 100 [‘very sedated’] mm) during the same relaxation period. These are two measures 
for assessing an individual’s level of sedation and will provide a subjective assessment of how 
sedated the subject is during the study.  These exploratory parameters will be summarized using 
descriptive statistics, and time course summaries of both scores will be generated for all 
treatments.  
7.4 Pharmacokinetic Analyses 
7.4.1 Plasma Pharmacokinetics 
PK parameters will be calculated for the different drugs and metabolites and study days based on 
data collected from the time of drug administration to the 24-h sample on the specified day.  Cmax 
and AUC (i.e. AUC3-24 for oxycodone and oxymorphone, AUC0-24 for paroxetine, escitalopram, 
and escitalopram metabolites) will be computed on the specified days (i.e., day 6, 12, and 21 for 
oxycodone and oxymorphone; day 5, 6, 11, 12, 20, and 21 for paroxetine, escitalopram, and 
escitalopram metabolites) as part of the exploratory endpoints for this study. Additionally, the 
following exploratory PK parameters will be determined for oxycodone, oxymorphone, 
paroxetine, escitalopram, and escitalopram metabolites on each specified day: 
x Time at which Cmax occurs (Tmax) 
x Elimination rate constant (Kel) 
x Terminal half-life (t1/2) 
x Accumulation ratio (for escitalopram and paroxetine) 
The PK parameters will be analyzed using noncompartmental methods based on actual sampling 
times. All parameters will be calculated using statistical software.  Serum concentrations below 
the limits of quantification will be set to zero for the purpose of this analysis (see Section 6).  Kel  
and t1/2 for each analyte and subject will only be included if the subject has 3 or more 
concentration values on the terminal portion of the pharmacokinetic curve and the linear 
regression of the log-concentration time curve has an adjusted coefficient of determination (R2) 
greater than 0.80.  
Oxycodone and oxymorphone Cmax and AUC will be log-transformed and the values from 
oxycodone alone versus oxycodone with either paroxetine or escitalopram will be compared 
using a linear mixed effects model (i.e., treatment as fixed effects and subject as random effects) 
to determine if oxycodone exposures differ between the two treatments on days 6, 12, and 21.  
The geometric mean ratio will be determined and no difference in exposure will be concluded if 
the two-sided 95% confidence interval includes 1.     
The PK parameters Cmax, AUCx-24, Tmax, and Kel will be summarized using descriptive statistics 
(number of subjects, geometric mean, mean, SD, coefficient of variation [CV], median, 
minimum, maximum, and interquartile range). Geometric mean and individual 


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concentration-time profiles will be presented in graphs. Descriptive statistics and comparisons 
between subgroups may be performed with respect to demographic variables (e.g., age, sex, 
weight, metabolizer phenotype). 
7.4.2 PK/PD Analyses 
A nonlinear-mixed effect PK/PD model will be developed for ǻVE55 versus time for all 
treatments. The model will be employed using statistical modeling software.  
PK models may be developed for each of the three drugs and metabolites evaluated in this study. 
Model structures will be selected based on previously published literature examples, visual 
inspection of the PK time course data, and diagnostic plots and objective function values from 
model fitting. The PK modeling may consider covariate exploration as well as fitting of 
metabolites for oxycodone and escitalopram that are analyzed.  
The PD modeling may use either predictions from the PK modeling or observed drug 
concentration data as input. Different PD model structures will be evaluated (e.g., effect 
compartment coupled to an indirect response model). Covariate exploration may be performed 
for the PD model based on demographic variables.  A separate modeling analysis plan will be 
developed for the planned PK/PD modeling analyses. 
7.5 Safety Analyses 
7.5.1 Adverse Events 
All adverse events (AEs) will be coded using the latest version of the Medical Dictionary for 
Regulatory Activities. The incidence of treatment-emergent adverse event (TEAEs), organized 
by system organ class and frequency, will be summarized by seriousness, severity, relationship 
to treatment, and by treatment at onset of the TEAE. A detailed listing of serious AEs and 
TEAEs leading to withdrawal will also be provided. 
7.5.2 Clinical Laboratory Tests 
Clinical laboratory results (hematology, serum chemistry, and urinalysis) will be summarized 
using descriptive statistics (number of subjects, mean, SD, minimum, median, and maximum). 
Clinical laboratory results will be classified as normal or abnormal, according to the reference 
ranges of the individual parameter. The number and percentage of subjects with abnormal 
laboratory results will be provided. No statistical testing will be performed on clinical laboratory 
data. 


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7.5.3 Vital Sign Measurements 
Vital sign measurements and changes from baseline will be summarized using descriptive 
statistics (number of subjects, mean, SD, minimum, median, and maximum) by treatment and 
time point. 
7.5.4 Safety 12-lead Electrocardiograms 
Safety 12-lead ECG data will be summarized using descriptive statistics (number of subjects, 
mean, SD, minimum, median, and maximum) by treatment and time point. 
7.5.5 Pulse Oximetry and Telemetry 
Continuous telemetry monitoring will be performed on days 5, 6, 11, 12, 20, and 21.  Events 
requiring intervention from the staff or discontinuation from the study will be recorded in 
appropriate logs. 
Oxygen saturation measurements obtained from 24-h pulse oximeters recordings will be used to 
plot time course profiles of oxygen saturation for treatments from  days 5, 6, 11, 12, 20, and 21.       
7.5.6 Physical Examinations 
Physical examination findings will be presented in a data listing, and abnormal physical 
examination findings will be recorded as AEs. 
7.5.7 Other Safety Data 
All concomitant medication usage and medications that changed in daily dose, frequency, or 
both since the subject provided informed consent will be summarized for each subject. 
8. Data Quality Assurance 
Completed electronic case report forms (eCRFs) are required for each subject randomly assigned 
to the study drug. Electronic data entry will be accomplished through the ClinSpark® remote 
electronic data capture system, which allows for on-site data entry and data management. This 
system provides immediate, direct data transfer to the database, as well as immediate detection of 
discrepancies, enabling site coordinators to resolve and manage discrepancies in a timely 
manner. Each person involved with the study will have an individual identification code and 
password that allows for record traceability. Thus, the system, and subsequently any 
investigative reviews, can identify coordinators, investigators, and individuals who have entered 
or modified records. 
Furthermore, the investigator retains full responsibility for the accuracy and authenticity of all 
data entered into the electronic data capture system. The completed dataset and their associated 
files are the sole property of the sponsor and should not be made available in any form to third 


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parties, except for appropriate governmental health or regulatory authorities, without written 
permission of the sponsor. 
 
 
 


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9. Appendices 
9.1 Randomization Schedule 
The study is a 3-period, double-blind, crossover study where subjects will be enrolled in cohorts 
of approximately 5.  Subjects will be randomized to one of six sequences (i.e., ABC, ACB, BAC, 
BCA, CAB, CBA) where treatment codes and interventions are summarized in the table below.  
Subjects will be randomized in blocks of 6. The remaining subject (i.e., 25th subject) will be 
assigned on of the six sequences randomly.   
The project biostatistician created the specifications for generating the randomization schedule as 
described above. A dummy randomization schedule generated in R.  The project biostatistician 
will transfer the program used to generate the ‘dummy’ schedule to the randomization 
biostatistician (unblinded), who is an independent party and will not be participating in any 
programming or statistical decisions for the study before breaking the blind. The randomization 
biostatistician will be responsible for generating the final randomization schedule. The output 
will be sent only to designated unblinded recipients. 
Table 1:  Treatment Codes and Treatment Names for SCR-012 
Treatment Code 
Treatment Name 
A 
Oxycodone/placebo 
B 
Oxycodone/paroxetine 
C 
Oxycodone/escitalopram 
 
 


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an opioid on ventilation 
 
 
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9.2 Nonlinear Regression Model 
The rebreathing procedure consists of three separate periods: i) breathing room air, termed 
‘relaxation’ period; ii) hyperventilation (primarily through deep breathing); and iii) rebreathing 
at one of 2 different isoxic end tidal PO2 (PetO2) (i.e., at 50 mm Hg and 150 mm Hg).  For the 
purposes of data analysis and determination of the primary endpoints, data from iii) will be used 
to estimate the ventilatory response to hypercapnia curve.  This relationship, which is 
characterized by a flat portion between minute ventilation and end-tidal PCO2 followed by a 
period of linear increase, can be represented using a hockey-stick function.  For purposes of 
these analyses, the following equation is pre-specified to describe data from the procedure: 
Vi = V0  (if PCO2  inflection point) 
Vi = V0 * (1 + ((PCO2,i – PCO2,inflection)*sslope /V0)g)1/g (if PCO2 > inflection point) 
Here, Vi is the minute ventilation that corresponds to an end-tidal CO2 of PCO2,i, V0 is baseline 
minute ventilation rate on the flat portion of the curve, PCO2,inflection is the end-tidal CO2 where 
increase from baseline minute ventilation begins, sslope is the slope of the curve, and g is a shape 
parameter in the hockey stick function that is set to 20 to provide the desired curvature.  Outlier 
measures, introduced by subject postural changes, sighing, talking, hiccups and other subject 
behaviors, will be identified based on evaluation of standardized residuals from the nonlinear 
regression (i.e., standardized residuals > 2 SD).  Coding for the nonlinear function will be 
performed in R.  An example of the coded function is provided below. 
ff <- function(p, v0, b, s) { 
  vs <- (p-b)*s 
  vs[which(vs<0)] <- 0 
  a <- 0.95 
  g <- 1/(1-a) 
  v <- v0*(1 + (vs/v0)**g)**(1/g) 
} 
 
fits<-function (x){ 
  nls(v ~ ff(p,v0,b,s), 
      lower=list(v0=5,  b=0,  s=0), 
      start=list(v0=8,  b=30,  s=1), 
      upper=list(v0=15, b=100, s=5), 
      trace=F, algorithm="port", data=x) 
} 
 


Statistical Analysis Plan  
SCR-012: Clinical study to investigate the effect of 
administration of selective serotonin reuptake inhibitors and 
an opioid on ventilation 
 
 
Page 25 of 25 
 
 
10. 
References 
Clinical Study to Investigate the Effect of the Combination of Psychotropic Drugs and an Opioid 
on Ventilation. Found at https://clinicaltrials.gov/ct2/show/NCT04310579. 
 
Duffin J, McAvoy GV. (1988). The peripheral-chemoreceptor threshold to carbon dioxide in 
man. J Physiol. 406:15-26. 
 
Mahamed S, Duffin J. (2001). Repeated hypoxic exposures change respiratory chemoreflex 
control in humans. J Physiol. 534(Pt. 2):595-603. 
 
van der Schrier R, Jonkman K, van Velzen M, Olofsen E, Drewes AM, Dahan A, Niesters M. 
(2017a). An experimental study comparing the respiratory effects of tapentadol and oxycodone 
in healthy volunteers. Br J Anaesth, 119(6), 1169-77. 
van der Schrier R, Roozekrans M, Olofsen E, Aarts L, van Velzen M, de Jong M, Dahan A, 
Niesters M. (2017b). Influence of Ethanol on Oxycodone-induced Respiratory Depression: A 
Dose-escalating Study in Young and Elderly Individuals. Anesthesiology, 126(3), 534-42. 
Johannesen, L., Vicente, J., Mason, J. W., Sanabria, C., Waite-Labott, K., Hongm M., Strauss, D. 
G. (2014) Differentiating drug-induced multichannel black on the electrocardiogram: 
randomized study of dofetilide, quinidine, ranolazine, and verapamil. Clinical Pharmacology & 
Therapeutics, 96(5), 549-558. 
 
Garnett C, Bonate PL, Dang Q, Ferber G, Huang D, Liu J, Mehrotra D, Riley S, Sager P, Tornoe 
C, Wang Y (2018). Scientific white paper on concentration-QTc modeling. J Pharmacokinet 
Pharmacodyn, 45(3):383-397. 
 
E14/S7B Questions and Answers: Clinical and nonclinical evaluation of QT/QTc Interval 
Prolongation and Proarrhythmic Potential. Found at 
https://database.ich.org/sites/default/files/E14-S7B_QAs_Step4_2022_0221.pdf