Pharmacokinetics of Polymyxin B in Adult Patients With Cystic Fibrosis
Conditions: Cystic Fibrosis, Polymyxin B
Sponsor: University of Michigan

 
 
 
 
 
 
 
Pharmacokinetics of Polymyxin B in Adult Patients with 
Cystic Fibrosis 
 
 
 
 
 
NCT04335370 
 
 
IRB Approval Date: December 4, 2019 
 
 

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Pharmacokinetics of Polymyxin B in Adult Patients with Cystic Fibrosis 
 
 
Contents   
1. Project Summary...........................................................................................................................2 
2. Abbreviations.................................................................................................................................2 
3. Background Information.................................................................................................................2 
4. Specific Aims / Hypothesis.............................................................................................................4 
5. Study Methodology........................................................................................................................4 
6. Data Analysis………………………….............................................................................................9 
7. Benefits and Risks.......................................................................................................................12 
8. Adverse Events............................................................................................................................13 
9. References..................................................................................................................................14 
10.  Appendices.................................................................................................................................16 
 
 

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1. Project Summary 
 
This is a single-center, open-label, non-interventional study to characterize the pharmacokinetics and 
safety of fixed-dose polymyxin B (PMB) in adult patients with cystic fibrosis (CF). 
 
2. Abbreviations 
 
 
ADL – activities of daily living 
AKI – acute kidney injury 
CF – cystic fibrosis 
FEV1 – forced expiratory volume in 1 second 
FiO2 – fraction of inspired oxygen 
GCS – Glasgow Coma Scale 
KDIGO – Kidney Disease: Improving Global Outcomes 
LC-MS/MS – liquid chromatography-tandem mass spectrometry 
MDR – multidrug-resistant 
NCI:CTCAE – National Cancer Institute: Common Terminology Criteria for Adverse Events 
PK – pharmacokinetics 
PMB – polymyxin B 
Scr – serum creatinine 
 
3. Background Information 
 
Cystic fibrosis is a genetic disease affecting multiple organ systems; however, pulmonary disease is the 
cause of the majority of morbidity and mortality.1 Pulmonary CF is a chronic, progressive disease process 
punctuated by episodes of acute exacerbation that require treatment. Pseudomonas aeruginosa is the 
predominant pathogen isolated in patients with acute exacerbations of cystic fibrosis, and guidelines from 
the Cystic Fibrosis Foundation recommend combination treatment directed against this pathogen as 
initial therapy.2 Such therapy traditionally consists of an antipseudomonal beta-lactam with either an 
antipseudomonal fluoroquinolone or an aminoglycoside.  
 
The demographics of patients with cystic fibrosis have shifted, and this shift has important implications 
for antimicrobial therapy. Once considered primarily a childhood disease, improvements in care have 
substantially increased the proportion of CF patients surviving into adulthood. In 1986, 70.8% of patients 
with CF were under 18 years of age. Data from  2016 CF Foundation Patient Registry Annual report show 
that that the majority of patients currently living with CF are adults (52.7%) and that median survival is 
now well into middle age (47.7 years).1 The prevalence of positive cultures for MDR P. aeruginosa is less 
than 10% in pediatric patients with CF, but increases steadily in to around 20% in adults age 30-40 years.1 
This increase in drug-resistance over time likely reflects recurrent exposure to antipseudomonal 
antibiotics resulting in a severely limited armamentarium of active antibiotics to treat these patients into 
adulthood.  
 
The polymyxins are cyclic peptide antibiotics which are positively charged at physiologic pH and exert 
bactericidal activity through binding to the lipopolysaccharide component of gram-negative bacterial 
membranes.3 Colistin, which is commercially available as the prodrug colistimethate sodium, has 
historically been the most commonly used polymyxin in patients with and without CF.4,5 There has been 
renewed interest into these compounds in the patients without CF due to the epidemic of antibiotic 
resistance. Population PK studies in critically ill patients have demonstrated high inter-patient variability 
in the exposure of formed colistin and inadequate attainment of therapeutic levels in patients with 
adequate or augmented renal function.6,7 The variability between patients in colistin exposure is due to 
variable conversion from colistimethate, which requires removal of five pro-drug functional groups, as 

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well as the differential pathways of elimination for colistimethate and formed colistin. Colistimethate is 
freely filtered and excreted in urine whereas formed colistin as avidly reabsorbed in the kidney and 
eliminated by non-renal mechanisms.8 The renal elimination of the inactive prodrug before conversion to 
the pharmacologically active form makes achieving colistin exposures associated with effective bacterial 
killing challenging in patients with adequate renal function. Patients with CF generally exhibit augmented 
clearance of renally eliminated compounds placing them at increased risk for underexposure.9 Polymyxin 
B, which is administered directly as active drug and reabsorbed in the kidney in a manner analogous to 
formed colistin, has demonstrated more consistent PK in critically ill patients.10-12  
 
The impact of patient-specific variables on the PK of the polymyxins has been an area of active 
investigation. As highlighted above, patient renal function has a significant bearing on the PK of colistin, 
through its prodrug colistimethate sodium, but has negligible impact on polymyxin B.10-12 Therefore, 
despite the fact that the polymyxin B label includes renal dose adjustments, this agent is dosed without 
respect to patient renal function in clinical practice.13 The only PK study of polymyxin B in patients with 
CF included 9 patients with only a median of 2 samples analyzed per patient (31 samples total).14 
Interestingly, this study did identify a relationship between polymyxin B CL and creatinine clearance; 
however, the validity and magnitude of this relationship are uncertain given that most of the observed 
effect was due to a single patient. The other patient-specific factor which has traditionally informed the 
dosing of these agents is patient body weight. Population PK studies of colistin from the modern era of 
use have challenged the traditionally held belief that the clearance and volume of distribution scale with 
patient weight.6,7 In fact, the updated European Medicines Agency labeling for colistin recommends fixed-
doses stratified by patient renal function based on these data.15 Similarly, the most recent PK studies of 
polymyxin B have failed to demonstrate an impact of patient body weight on the clearance of polymyxin 
B; however, the majority of polymyxin B dosing in clinical practice is still weight-based.11,12   
 
The polymyxins are associated with significant toxicities, namely, nephrotoxicity and neurotoxicity, which 
limit their clinical use. Therefore, it is important to assess the relative toxicity of colistin and PMB to ensure 
that shifting use to PMB for its PK advantages does not lead to increased toxicity. The comparative 
nephrotoxic potential of colistin and polymyxin B has been extensively investigated in non-CF 
populations, primarily the critically ill, and a meta-analysis of recent observational studies found an 
increased risk for acute kidney injury (AKI) with colistin relative to polymyxin B (RR 1.55, 95% CI 1.36-
1.78).16 Only two studies assessing nephrotoxicity of both colistin and polymyxin B have included patients 
with CF. Phe and colleagues included 38 patients with CF and found that CF was actually protective 
against colistin associated AKI (aOR 0.03, 95% CI 0.001-0.79) in multivariable analysis.17 Unfortunately, 
no CF patients in this study received polymyxin B, so the relative rates of kidney injury between the two 
agents in this population could not be assessed. A 2017 study investigated the association between 
polymyxin treatment and kidney injury in 220 adult CF patients, 29 treated with PMB and 191 treated with 
colistin.18 The study found no difference in rates of AKI between PMB and colistin (34.5% vs 29.8%, p = 
0.77) in patients nor in the rates of renal recovery by hospital discharge (90.0% vs 91.2%, p = 1.00). 
Neurotoxicity with the polymyxins are poorly characterized in patients with and without CF, especially 
with polymyxin B. Studies with colistin in pediatric patients with CF have found rates of neurotoxicity 
between 0 – 97.3% with many demonstrating higher rates of neurotoxicities than AKI.5 The most common 
manifestation of neurotoxicity with polymyxins is mild-moderate perioral paresthesia followed by 
weakness, ataxia, and in rare cases respiratory compromise.5,19,20 Neurotoxicity has not been evaluated 
in studies comparing colistin and PMB.   
 
We propose to measure the plasma concentrations of PMB in adult patients with CF receiving intravenous 
therapy as a part of their routine care and to use these measured concentrations to build population 
pharmacokinetic models. The population pharmacokinetic modeling approach will allow the assessment 
of the impact of patient specific covariates (i.e. weight, renal function) on pharmacokinetic parameters. 
Patients will be monitored for nephrotoxicity and neurotoxicity to ensure that PMB has an acceptable 

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margin of safety in this patient population. This investigation will be the first to prospectively assess the 
pharmacokinetics and toxicities of PMB in this patient population and will facilitate optimal use of this 
compound in the management of acute pulmonary exacerbations of CF. 
 
4. Specific Aim/Hypothesis 
 
4.1. Measure the plasma concentration of PMB in adult CF patients receiving intravenous 
therapy. Adult patients with CF often receive multiple courses of antipseudomonal antibiotics 
over the course of their disease resulting in the evolution of multi-drug resistant (MDR) P. 
aeruginosa pulmonary colonizers. The polymyxins, colistin and PMB, frequently retain activity 
against MDR gram-negative bacteria. Colistin has historically been the most commonly used 
polymyxin in patients with CF; however, new pharmacokinetic (PK) and toxicity data obtained 
from non-CF populations suggest that PMB may achieve more consistent exposure with lower 
associated toxicity. We aim to measure concentrations of PMB in plasma samples obtained from 
adult CF patients treated with polymyxin B using liquid chromatography–tandem mass 
spectrometry (LC-MS/MS). 
4.2. Characterize the pharmacokinetics of PMB in adult CF patients. There are three major 
population PK studies which inform the dosing of PMB and one small study including patients 
with CF. These studies suggest that the clearance of PMB is not related to patient body weight 
and have discordant results regarding patient renal function. Therefore, underweight patient 
populations with excellent renal function, such as CF, may be at risk for underdosing with 
traditional weight-based regimens. We aim to use population pharmacokinetic modeling to 
characterize the PK of fixed-dose PMB in this special population and assess the effect of patient-
specific covariates (e.g., body weight, renal function) on PK parameters. 
4.3. Determine the safety of PMB therapy in adult CF patients. Polymyxin use is limited to salvage 
therapy for MDR gram-negative bacterial infections and cases of allergy, intolerance, or adverse 
effects to alternative agents due to the significant toxicities related to these compounds. 
Nephrotoxicity is the most common dose-limiting toxicity; however, it has been poorly 
characterized with PMB in patients with CF. Neurotoxicity has also been reported and occurs 
with moderate frequency with colistin in studies of patients with CF. We aim to characterize PMB-
associated nephrotoxicity using the Kidney Disease: Improving Global Outcomes (KDIGO) 
criteria and neurotoxicity via patient self-report. 
5. Study Methodology 
 
5.1. Study design: Single-center, open-label, non-interventional, pharmacokinetic study. 
 
5.2. Inclusion criteria: Study subjects will be identified by investigators in the course of providing 
clinical care or by means of reports built in TheraDoc® Clinical Surveillance software (version 
4.4; Premier Inc, Salt Lake City, UT) or built directly into the electronic medical record (EPIC 
Systems, Madison, WI). Subjects fulfilling the following criteria will be eligible for inclusion: 
 
5.2.1. Adults, greater than 18 years of age 
 
5.2.2. Diagnosed with cystic fibrosis 
 
5.2.3. Treated with intravenous polymyxin B for a suspected or confirmed infection as part of 
routine care 
 

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5.3. Exclusion criteria 
 
5.3.1. Extra-corporeal organ support systems that would alter drug distribution including renal 
replacement (e.g., hemodialysis, peritoneal dialysis, continuous renal replacement) or 
extra-corporeal membrane oxygenation 
 
5.3.2. Pregnancy  
 
5.3.3. Unable to provide informed consent 
 
5.4.  Study Timeline 
 
 
Figure 1: Study Timeline and Procedures. Abbreviations: CF, cystic fibrosis; LC-MS/MS, liquid 
chromatography tandem mass spectrometry, Scr, serum creatinine 
 
 
5.5. Informed Consent 
 
5.5.1. Procedures: A member of the study team will review the study and informed consent 
with the potential participant and answer any questions. Written informed consent will be 
obtained from the patient prior to enrollment in the study. Informed consent documents will 
outline the risk associated with obtaining the blood samples as well as the anticipated 
benefits of the study. A copy of the signed informed consent will be given to the participant. 
Subjects will be free to opt out of the study at any time for any reason after enrollment. 
 
5.5.2. Storage: Informed consent documents will be stored in a locked cabinet in a locked 
office. Copies of the informed consent documents will be uploaded onto M+Box with 
access restricted to IRB-authorized study personnel, and will also be uploaded to 
participant’s medical record in MiChart.  
 
5.6. Dosing and Administration 

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5.6.1. The dose and duration of infusion for PMB will determined at the discretion of the 
prescribing physician in the course of routine clinical care. There is no study intervention 
on the dosing and administration of PMB.  
 
5.6.2. The recommended dosing schedule for intravenous polymyxin B at Michigan Medicine 
consists of an initial weight-based loading dose (2 mg/kg, maximum of 200 mg) followed by 
100 mg every 12 hours for the duration of therapy as determined by the clinician. A 
reduction of the maintenance dose to 75 mg every 12 hours is recommended for patients 
with total body weight less than or equal to 50 kg.  
 
5.7. Sampling: 
 
5.7.1. Blood samples will be collected from enrolled patients at 5 time points during a single 
dosing interval under steady-state conditions. Sampling will occur on any day of therapy 
immediately prior to and following a single dose of PMB. The infusion time is selected at 
the discretion of the prescribing physician; thus the sampling schema is described based 
on the duration of infusion (Table 1). 
 
Table 1: Sample collection times 
Sample Code 
Collection Timepoint 
Collection Time Relative to 
Duration of Infusion (tinf) 
C0 
Prior to Start of Infusion 
0 hour 
C1 
End of Infusion 
tinf + 0 hour 
C2 
One Hour after End of Infusion 
tinf + 1 hour 
C3 
Three Hours after End of Infusion 
tinf + 3 hours 
C4 
Eight Hours 
8 hours 
 
5.7.2. Blood samples will be collected via one of three sampling methodologies: peripheral 
venipuncture, peripheral intravenous catheter, or a central venous catheter (e.g., PICC, 
Port). The method of obtaining blood samples will be determined by study personnel and 
will consider patient preference, patient safety, and the likelihood of obtaining adequate 
samples. Insertion of, care for, and sampling from indwelling catheters will be performed 
per hospital policy.   
 
5.7.3. The procedure for obtaining and processing blood samples can be found in the 
Laboratory Protocol document in the Appendix (10.1). 
 
5.8. Demographic and Clinical data: Study team members will obtain demographic and clinic data 
needed to describe the study population and build pharmacokinetic models. Data will be 
abstracted from DataDirect or obtained directly from the medical record for each index 
encounter. Data recorded directly from the medical record will be stored in REDcap. 
 
5.8.1. Demographic: comprehensive demographic data will be obtained from DataDirect. 
Examples of variables of interest include race and sex. 
 
5.8.2. Encounter: comprehensive encounter data will be obtained from DataDirect. Example 
variables of interest include age, weight, height, body mass index, admission and 
discharge dates, and sites of care. 
 

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5.8.3. Diagnosis: comprehensive codified diagnosis data will be obtained from DataDirect. 
Example diagnoses of interest include comorbid conditions, admission diagnoses, and 
discharge diagnoses  
 
5.8.4. Procedures: comprehensive procedure data will be obtained from Data Direct. Example 
variables of interest include procedure codes related to renal replacement therapy or 
source control procedures 
 
5.8.5. Medications: comprehensive medication orders and administration data will be obtained 
from DataDirect. Example medications of interest include polymyxin B, aminoglycosides, 
beta-lactams, other anti-infectives, vasopressors, albumin, fluid, immunosuppressants, 
corticosteroids, intravenous contrast dye, and chemotherapies 
 
5.8.6. Laboratory: comprehensive laboratory information, including microbiology, will be 
obtained from DataDirect. Example laboratory values of interest include aminoglycoside or 
vancomycin drug concentrations, serum creatinine, blood urea nitrogen, sodium, 
potassium, CO2, albumin, total bilirubin, white blood cell count, platelet count, hemoglobin, 
hematocrit, total lymphocyte count, pH, PaO2, bicarbonate, procalcitonin, erythrocyte 
sedimentation rate, c-reactive protein, and culture results. 
 
5.8.7. Vitals: comprehensive vital signs and fluid inputs and outputs will be obtained from 
DataDirect. Example vitals of interest include mechanical ventilation, fraction of inspired 
oxygen (FiO2), oxygen saturation, temperature, blood pressure, heart rate, respiratory rate, 
urine output, Glasgow Coma Scale score (GCS), dietary information.  
 
5.8.8. Outcome: hospital length of stay, mortality, readmission rate. Results of spirometry, 
including forced expiratory volume in 1 second (FEV1). 
 
5.9. Assay: Plasma concentrations of polymyxin B, comprising both polymyxin B1 and B2 
components, will be determined using LC-MS/MS.  
 
5.10. 
Storage of data and samples 
 
5.10.1. Sample storage: Samples will be labeled with a unique study identifier and stored at -80 
C. No protected health information will be stored with the samples. Access to samples will 
be restricted to authorized research personnel.  
 
5.10.2. Data storage: Sample information including subject name, medical record number, and 
date and time of collection will be recorded separately in the sample collection log. The 
sample collection log will be stored in a locked draw within a locked office, accessible only 
to study personnel. Electronic data will be maintained in a password-protected file within 
M+box. Access to this document will be restricted to approved members of the research 
team. Only codified data will be used in analysis.  
 
5.11. 
Patient reimbursement: Patients will be reimbursed $100 for participation in the study. 
 
6. Data Analysis 
 
6.1. Population Pharmacokinetic Analysis 
 

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6.1.1. Pharmacokinetic Modeling: The PK data will be analyzed using a population PK 
modeling approach through the nonparametric adaptive grid (NPAG) algorithm in the 
PmetricsTM package for the R environment.21,22 Models will be parameterized as one- and 
two-compartment systems with zero-order infusion and elimination from the central 
compartment modeled as a first-order process. Michaelis-Menten and mixed-order 
linear/Michaelis Menten elimination will be tested if first-order processes alone do not 
display adequate fit of the data. 
 
For all models, the inverse of the estimated assay variance will be used as the first 
estimate for weighting. Weighting will be accomplished by making the assumption that total 
observation variance is proportional to assay variance. Assay variance will be determined 
on a between-day basis. The analysis will be performed with adaptive γ, a scalar which is 
optimized with each cycle to produce the best approximation to the homoscedastic 
assumption. 
 
Models will be run for at least 100 cycles and Bayesian estimates will be obtained for each 
patient. For each model, both the mean and median will be employed as measures of 
central tendency for the population parameter estimates and will be evaluated in the 
Bayesian analysis. Scatter plots will be examined for individual patients and for the 
population as a whole.  
 
6.1.2. Monte Carlo Simulation: The parameter vector and covariance matrix from population 
PK modeling will be used as the prior distribution for the simulation function within 
PmetricsTM. 1000-subject Monte Carlo simulations will be performed for candidate dosing 
regimens. 
 
The simulated plasma concentration-time curves will be used to calculate area under the 
concentration-time curve (AUC) values for different 24-hour increments through 96 hours. 
For each regimen examined, probability of efficacy will be the fraction of the simulated 
subjects at each time interval for which the 24-hour AUC is between 50 – 100 mg*h/L while 
the probability of toxicity will be the fraction of subjects with 24-hour AUC values ≥ 100 
mg*h/L.23,24  
 
6.2. Toxicity Analysis 
 
6.2.1. Nephrotoxicity: Nephrotoxicity will be assessed using the KDIGO criteria to define AKI. 
The nephrotoxicity endpoint will be met if subjects meet criteria for any stage of AKI by the 
KDGIO criteria using measured serum creatinine (Table 2). The degree of AKI will also be 
described by KDIGO stage. Time to renal recovery after cessation of PMB and the 
proportion of patients with renal recovery by hospital discharge will also be assessed. 
Renal recovery is defined as resolution of all KDIGO criteria for AKI.  
 
Table 2: Definition of AKI using the KDGIO criteria 
Stage 
 
Serum Creatinine  
 
1 
1.5 – 1.9 x baseline 
OR 
≥ 0.3 mg/dL increase from baseline 
2 
2.0 – 2.9 x baseline 
3 
≥ 3.0 x baseline 
OR 

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≥ 4 mg/dL 
OR  
Initiation of renal replacement therapy 
 
 
6.2.2. Neurotoxicity: Neurotoxicities will be assessed by patient self-report. The type of 
toxicity, anatomic site of toxicity, and severity will be assessed by the study personnel 
using the National Cancer Institute: Common Terminology Criteria for Adverse Events 
(NCI:CTCAE) scale.25  
 
 
         Table 3: NCI:CTCAE terminology and definitions for potential neurotoxicities 
CTCAE Term 
Definition 
Apnea 
A disorder characterized by cessation of breathing 
Ataxia 
A disorder characterized by lack of coordination of muscle movements 
resulting in the impairment or inability to perform voluntary activities 
Confusion 
A disorder characterized by a lack of clear and orderly thought and 
behavior 
Dizziness 
A disorder characterized by a disturbing sensation of lightheadedness, 
unsteadiness, giddiness, spinning, or rocking 
Dyspnea 
A disorder characterized by an uncomfortable sensation of difficulty 
breathing 
Hallucinations A disorder characterized by a false sensory perception in the absence 
of an external stimulus 
Hearing 
impairment 
A disorder characterized by partial or complete loss of the ability to 
detect or understand sounds resulting from damage to ear structures 
Muscle 
Weakness 
A disorder characterized by a reduction in the strength of muscles in 
multiple anatomic sites 
Paresthesia 
A disorder characterized by functional disturbances of sensory neurons 
resulting in abnormal cutaneous sensations of tingling, numbness, 
pressure, cold, and/or warmth 
Peripheral 
motor 
neuropathy 
A disorder characterized by damage or dysfunction of peripheral motor 
nerves 
Peripheral 
sensory 
neuropathy 
A disorder characterized by damage or dysfunction of peripheral 
sensory nerves 
Psychosis 
A disorder characterized by personality change, impaired functioning, 
and loss of touch with reality.  
Respiratory 
Failure 
A disorder characterized by impaired gas exchange by the respiratory 
system resulting in hypoxia and a decrease in oxygenation of the 
tissues that may be associated with an increase in arterial levels of 
carbon dioxide 
Seizure 
A disorder characterized by sudden, involuntary skeletal muscle 
contractions of cerebral or brain stem origin 
 
 
         Table 4: NCI:CTCAE terminology and grade for potential neurotoxicities 
CTCAE 
Term 
Grade 1 
Grade 2 
Grade 3 
Grade 4 
Grade 5 
Apnea 
- 
- 
Present; 
medical 
Life-threatening 
respiratory or 
Death 

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intervention 
indicated 
hemodynamic 
compromise; 
intubation or 
urgent 
intervention 
indicated 
Ataxia 
Asymptomatic; 
clinical or 
diagnostic 
observations 
only 
Moderate 
symptoms; 
limiting 
instrumental 
ADL 
Severe 
symptoms, 
limiting self-
care ADL; 
mechanical 
assistance 
indicated 
- 
- 
Confusion 
Mild 
disorientation 
Moderate 
disorientation; 
limiting 
instrumental 
ADL 
Severe 
disorientation; 
limiting self-
care ADL 
Life-threatening 
consequences; 
urgent 
intervention 
indicated 
- 
Dizziness 
Mild 
unsteadiness 
or sensation of 
movement 
Moderate 
unsteadiness 
or sensation of 
movement; 
limiting 
instrumental 
ADL 
Severe 
unsteadiness 
or sensation of 
movement; 
limiting self-
care ADL 
- 
- 
Dyspnea 
Shortness of 
breath with 
moderate 
exertion 
Shortness of 
breath with 
minimal 
exertion; 
limiting 
instrumental 
ADL 
Shortness of 
breath at rest; 
limiting self-
care ADL 
Life-threatening 
consequences; 
urgent 
intervention 
indicated 
Death 
Hallucinations 
Mild 
hallucinations 
(e.g. perceptual 
distortions) 
Moderate 
hallucinations 
Severe 
hallucinations; 
hospitalization 
not indicated 
Life-threatening 
consequences; 
threats of harm 
to self or 
others; 
hospitalization 
indicated 
Death 
Hearing 
Impairment 
Subjective 
change in 
hearing in the 
absence of 
documented 
hearing loss 
Hearing loss 
with hearing 
aid or 
intervention not 
indicated; 
limiting 
instrumental 
ADL 
Hearing loss 
with hearing 
aid or 
intervention 
indicated; 
limiting self-
care ADL 
Decrease in 
hearing to 
profound 
bilateral loss; 
nonservicable 
hearing 
- 
Muscle 
weakness 
Symptomatic; 
perceived by 
patient but not 
evident on 
physical exam 
Symptomatic; 
evident on 
physical exam; 
limiting 
instrumental 
ADL 
Limiting self-
care ADL 
- 
- 
Paresthesia 
Mild symptoms 
Moderate 
symptoms; 
limiting 
instrumental 
ADL 
Severe 
symptoms, 
limiting self-
care ADL 
- 
- 
Peripheral 
motor 
neuropathy 
Asymptomatic; 
clinical or 
diagnostic 
Moderate 
symptoms; 
limiting 
Severe 
symptoms, 
limiting self-
care ADL 
Life-threatening 
consequences; 
urgent 
Death 

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observations 
only 
instrumental 
ADL 
intervention 
indicated 
Peripheral 
sensory 
neuropathy 
Asymptomatic 
Moderate 
symptoms; 
limiting 
instrumental 
ADL 
Severe 
symptoms, 
limiting self-
care ADL 
Life-threatening 
consequences; 
urgent 
intervention 
indicated 
- 
Psychosis 
Mild psychotic 
symptoms 
Moderate 
psychotic 
symptoms (e.g. 
disorganized 
speech; 
impaired reality 
testing) 
Severe 
psychotic 
symptoms (e.g. 
paranoid, 
extreme 
disorganization
); 
hospitalization 
not indicated, 
new onset 
Life-threatening 
consequences, 
threats of harm 
to self or 
others; 
hospitalization 
indicated 
Death 
Respiratory 
Failure 
- 
- 
- 
Life-threatening 
consequences; 
urgent 
intervention, 
intubation, or 
ventilator 
support 
indicated 
Death 
Seizure 
Brief partial 
seizure and no 
loss of 
consciousness 
Brief 
generalized 
seizure 
New onset 
seizures 
(partial or 
generalized); 
multiple 
seizures 
despite medical 
intervention 
Life-threatening 
consequences; 
prolonged 
repetitive 
seizures 
Death 
 
         Abbreviations: ADL, activities of daily living 
 
          *Instrumental ADL refer to preparing meals, shopping for groceries or clothes, using the telephone,  
 
           managing money, etc. 
 
          **Self-care ADL refer to bathing, dressing and undressing, feeding self, using the toilet, taking 
 
           medications, and not bedridden 
 
6.3. Statistical Analysis 
 
6.3.1. Baseline demographic and clinical data: Baseline demographic and clinical data will 
be assessed using descriptive statistics. Variables will be summarized as mean (standard 
deviation), median (5th, 95th percentile), or number (percentage) as indicated.  
 
6.3.2. Population pharmacokinetic analysis: Model goodness-of-fit of the observed data will 
be assessed by regression with an observed-predicted plot. Between-subject variability will 
be quantified using coefficients of determination. Model discrimination will be based on log-
likelihood (-2LL) and Akaike’s Information Criterion (AIC) objective function values as well 
as diagnostic plots. Predictive performance evaluation will be based on weighted mean 
bias and the bias-adjusted weighted mean precision.  
  
6.3.3. Toxicity analysis: Nephrotoxicity and neurotoxicity rates will be summarized as number 
(percentage). Time to renal recovery will be summarized as mean (standard deviation) or 
median (interquartile range) days as indicated while renal recovery by hospital discharge 
will be summarized as number (percentage).  
 

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7. Benefits and Risks 
 
7.1. Benefits:  
 
7.1.1. Current CF Foundation guidelines recommend that two antibiotics with activity against P. 
aeruginosa as the standard of care for treatment of acute pulmonary exacerbations. Many 
adult CF patients have had extensive lifetime exposure to antipseudomonal antibiotic 
therapy and may require therapy with last line agents due to multi-drug resistance in 
clinical isolates. The polymyxins, colistin and polymyxin B, are often required as 
combination salvage therapy for isolates with documented resistance to aminoglycosides 
or fluoroquinolones. Polymyxin B has significant pharmacokinetic advantages to colistin for 
CF patients; however, limited data exist in this patient subpopulation to guide dosing in 
practice. The data generated by this study will be used to confirm dosing of polymyxin B in 
this population and ensure safety with commonly administered doses extrapolated from 
non-CF patient populations. There is no direct benefit to patients enrolled in the study at 
the time of enrollment; however, patients treated with polymyxin B at the time of the study 
are at risk for re-infection with MDR organisms in the future. Therefore, PK data obtained 
in this study could inform the dosing of polymyxin B for the treatment of future infections 
with MDR organisms. 
 
7.1.2. Patients will not experience direct benefit from this study. Patients will not be informed of 
study results. 
 
7.2. Risks 
 
This study poses no more than minimal risk to participants. Potential risks are as follows. 
 
7.2.1. Accidental Disclosure of Protected Health Information (PHI) 
 
7.2.1.1. 
Frequency: Rare 
 
7.2.1.2. 
This investigation will involve the use of PHI. With any use of PHI, the potential 
for accidental disclosure exists.  
 
7.2.2. Adverse Effects Due to Blood Sampling 
 
7.2.2.1. 
Frequency: Rare 
 
7.2.2.2. 
The only intervention outside of routine care in this study is blood sampling. 
Potential adverse effects of blood sampling include mild pain, anxiety/fear, bruising, 
hematoma, arterial puncture, nerve damage, re-bleeding, phlebitis, or vasovagal 
reactions.  
 
7.3. Protection Against Risks 
 
7.3.1. Accidental Disclosure of Protected Health Information (PHI) 
We will follow standard practice for protecting research data (locked cabinets/offices 
requiring key access, restricted access, use of secure servers). Protection of participant 
confidentiality will be maintained by providing each subject a unique identification 
number.  Only this number will be used on study documents that relate to the subject. All 
physical data will be stored in a locked cabinet within a locked office. Electronic study 

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data will be maintained on University of Michigan servers in M+Box and accessed 
through University devices or VPN. Access to PHI will be restricted to IRB-approved 
study personnel. All data will be codified prior to analysis. 
 
7.3.2. Adverse Effects Due to Blood Sampling 
To minimize the risks associated with blood sampling, blood samples will be obtained by 
a member of the study team who has received training specific to blood sampling. Best 
practice procedures for phlebotomy will be followed. A maximum of 5 mL of blood will be 
removed per sample for a maximum total volume of 30 mL per patient, which is less than 
10% of the volume removed in a standard blood donation. When possible, existing 
indwelling central venous access will be used to obtain samples to avoid additional 
venipuncture. 
 
8. Adverse Events 
 
8.1. Reporting Plan 
We will utilize a study specific adverse event (AE) reporting plan and only report adverse 
events directly related to the venipuncture or venous access to the IRB per the recommended 
guideline. 
 
8.2. Other Reportable Information or Occurrence 
Any breach of confidentiality will be reported immediately to the IRB. 
 
 
 

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9. References 
 
1. 
Cystic Fibrosis Foundation. Cystic Fibrosis Foundation Patient Registry 2016 Annual Report. 
Cystic 
Fibrosis 
Foundation 
website. 
https://www.cff.org/Research/Researcher-
Resources/Patient-Registry/2016-Patient-Registry-Annual-Data-Report.pdf. Accessed January 
02, 2018. 
2. 
Flume PA, Mogayzel PJ, Jr., Robinson KA, et al. Cystic fibrosis pulmonary guidelines: treatment 
of pulmonary exacerbations. Am J Respir Crit Care Med. 2009;180(9):802-808. 
3. 
Nation RL, Velkov T, Li J. Colistin and polymyxin B: peas in a pod, or chalk and cheese? Clin 
Infect Dis. 2014;59(1):88-94. 
4. 
Li J, Nation RL, Turnidge JD, et al. Colistin: the re-emerging antibiotic for multidrug-resistant 
Gram-negative bacterial infections. Lancet Infect Dis. 2006;6(9):589-601. 
5. 
Young DC, Zobell JT, Waters CD, et al. Optimization of anti-pseudomonal antibiotics for cystic 
fibrosis pulmonary exacerbations: IV. colistimethate sodium. Pediatr Pulmonol. 2013;48(1):1-7. 
6. 
Garonzik SM, Li J, Thamlikitkul V, et al. Population pharmacokinetics of colistin methanesulfonate 
and formed colistin in critically ill patients from a multicenter study provide dosing suggestions for 
various categories of patients. Antimicrob Agents Chemother. 2011;55(7):3284-3294. 
7. 
Nation RL, Garonzik SM, Thamlikitkul V, et al. Dosing guidance for intravenous colistin in critically-
ill patients. Clin Infect Dis. 2017;64(5):565-571. 
8. 
Zavascki AP, Nation RL. Nephrotoxicity of Polymyxins: Is There Any Difference between 
Colistimethate and Polymyxin B? Antimicrob Agents Chemother. 2017;61(3). 
9. 
Rey E, Treluyer JM, Pons G. Drug disposition in cystic fibrosis. Clin Pharmacokinet. 
1998;35(4):313-329. 
10. 
Sandri AM, Landersdorfer CB, Jacob J, et al. Population pharmacokinetics of intravenous 
polymyxin B in critically ill patients: implications for selection of dosage regimens. Clin Infect Dis. 
2013;57(4):524-531. 
11. 
Miglis C, Rhodes NJ, Avedissian SN, et al. Population Pharmacokinetics of Polymyxin B in 
Acutely Ill Adult Patients. Antimicrob Agents Chemother. 2018;62(3). 
12. 
Manchandani P, Thamlikitkul V, Dubrovskaya Y, et al. Population Pharmacokinetics of Polymyxin 
B. Clin Pharmacol Ther. 2017. 
13. 
Polymyxin B Sulfate [package insert]. Bedford Laboratories, Bedford, OH; June 2011. 
14. 
Avedissian S, Miglis C, Kubin CJ, et al. Polymyxin B Pharmacokinetics in Adult Cystic Fibrosis 
Patients. Pharmacotherapy. 2018. 
15. 
Nation RL, Garonzik SM, Li J, et al. Updated US and European Dose Recommendations for 
Intravenous Colistin: How Do They Perform? Clin Infect Dis. 2016;62(5):552-558. 
16. 
Vardakas KZ, Falagas ME. Colistin versus polymyxin B for the treatment of patients with 
multidrug-resistant Gram-negative infections: a systematic review and meta-analysis. Int J 
Antimicrob Agents. 2017;49(2):233-238. 
17. 
Phe K, Lee Y, McDaneld PM, et al. In vitro assessment and multicenter cohort study of 
comparative nephrotoxicity rates associated with colistimethate versus polymyxin B therapy. 
Antimicrob Agents Chemother. 2014;58(5):2740-2746. 
18. 
Crass RL, Rutter WC, Burgess DR, Martin CA, Burgess DS. Nephrotoxicity in Patients with or 
without Cystic Fibrosis Treated with Polymyxin B Compared to Colistin. Antimicrob Agents 
Chemother. 2017;61(4). 
19. 
Koch-Weser J, Sidel VW, Federman EB, Kanarek P, Finer DC, Eaton AE. Adverse effects of 
sodium colistimethate. Manifestations and specific reaction rates during 317 courses of therapy. 
Ann Intern Med. 1970;72(6):857-868. 
20. 
Falagas ME, Kasiakou SK. Toxicity of polymyxins: a systematic review of the evidence from old 
and recent studies. Crit Care. 2006;10(1):R27. 

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21. 
Neely MN, van Guilder MG, Yamada WM, Schumitzky A, Jelliffe RW. Accurate detection of 
outliers and subpopulations with Pmetrics, a nonparametric and parametric pharmacometric 
modeling and simulation package for R. Ther Drug Monit. 2012;34(4):467-476. 
22. 
R Core Team (2017). R: a language and environment for statistical computing. R Foundation for 
Statistical Computing, Vienna, Austria. URL https://www.R-project.org/. 
23. 
Dudhani RV, Turnidge JD, Nation RL, Li J. fAUC/MIC is the most predictive 
pharmacokinetic/pharmacodynamic index of colistin against Acinetobacter baumannii in murine 
thigh and lung infection models. J Antimicrob Chemother. 2010;65(9):1984-1990. 
24. 
Cheah SE, Li J, Tsuji BT, Forrest A, Bulitta JB, Nation RL. Colistin and Polymyxin B Dosage 
Regimens against Acinetobacter baumannii: Differences in Activity and the Emergence of 
Resistance. Antimicrob Agents Chemother. 2016;60(7):3921-3933. 
25. 
National Cancer Institute. Common Terminology Criteria for Adverse Events (CTCAE) Version 
5.0. 
Cancer 
Therapy 
Evaluation 
Program 
website. 
https://ctep.cancer.gov/protocoldevelopment/electronic_applications/ctc.htm#ctc_50. Published 
27 Nov 2017, Accessed 03 May 2018. 
 
 
 

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10. Appendices 
10.1. 
Appendix I: Laboratory Protocol 
Laboratory Protocol 
1. Blood Collection Tubes 
 
Plastic Lavender Top K2-EDTA Tube (BD, Franklin Lakes, NJ, Catalog# 367863) 
 
2. Blood Collection Supply Quantities 
Five blood samples are to be obtained and processed per subject on polymyxin B therapy. Samples will 
be collected at the time points listed below relative to the end of polymyxin B infusion (tinf) 
Sample 
Code 
Collection Timepoint 
Collection Time Relative to 
Duration of Infusion (tinf) 
C0 
Prior to Start of Infusion 
0 hour 
C1 
End of Infusion 
tinf + 0 hour 
C2 
One Hour after End of Infusion 
tinf + 1 hour 
C3 
Three Hours after End of Infusion 
tinf + 3 hours 
C4 
Eight Hours 
8 hours 
 
Minimum Supplies Necessary: 
Up to 20 subjects × 5 blood collection tubes = 
 
 
100 Blood Collection Tubes 
100 blood samples x 2 plasma aliquots/blood sample= 
200 cryovials (Screw Capped 
Polypropylene, 1-2 mL) 
200 cryovials × 1box/81 cryovials=   
 
 
 
3 cryovial storage boxes 
 
3. Pre-Study Preparation 
a. Plasma collection tubes 
i. Label 5 plasma collection tubes per subject with: 
1) study protocol number 
2) the study subject code 
a) color code with a highlighter pen (yellow, pink, green, orange) the 
subject code if more than one subject is to be studied on the same 
date 
3) date of collection 

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4) sample code (i.e. C0, C1, etc.) 
ii. Transfer plasma collection tubes to a test-tube rack 
1) Individual test-tube racks should be used for each subject if more than 
one subject is to be studied on the same day 
iii. Pre-chill (2-8°C) plasma collection tubes prior to blood collection 
 
b. Cryovials 
i. Label 10 cryovials per subject with: 
1) study protocol number 
2) the study subject code 
a) color code with a highlighter pen (yellow, pink, green, orange) the 
subject code if more than one subject is to be studied on the same 
date 
b) the color code should match the plasma collection tube for each 
subject to reduce the risk of potential transfer error 
3) date of collection 
4) sample code (i.e. C0, C1, etc.) 
5) aliquot number (AQ-1, AQ-2) 
ii. Transfer cryovials to a rack 
1) Individual cryovial racks should be used for each subject if more than one 
subject is to be studied on the same day 
 
c. Cryovial boxes 
i. Label 2 cryovial boxes with: 
1) study protocol number 
2) date of collection 
3) aliquot number (AQ-1 and AQ-2) 
 
4. Blood Sample Collection and Processing 
a. Collection 
i. Collect venous blood in pre-labeled and chilled lavender top plasma collection tubes 
ii. Invert the plasma collection tube ten times slowly and gently to ensure adequate 
mixing of the EDTA with the sample 
iii. Immediately replace the sample tube upright in the test-tube rack within the study 
cooler  
iv. Record actual time of sample collection in sample collection log 
 
b. Processing 
i. Centrifuge the whole blood at 3000 rpm for 12 minutes in a refrigerated centrifuge 
set to 4°C 
ii. Transfer the supernatant (plasma) to pre-labeled cryovials in 0.5 – 1 mL aliquots of 
equal volume, taking care not to disturb the buffy coat.  
1) See the section below for management of insufficient sample volume 
iii. Place cryovials into the appropriate cryovial boxes ordered by subject and sample 
code 

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1) More than one subject can be stored in each cryovial box. Do not divide a 
samples for a single subject between more than one cryovial box 
iv. Store cryovial boxes at -80°C until analysis  
1) The time from blood collection until the plasma sample is stored at -80°C 
should be 90 minutes or less. 
 
c. Potential Problems 
i. Hemolysis 
1) Samples with visible hemolysis may be processed as noted  
2) The cryovials for hemolyzed samples should be marked with the term “Hemo” 
 
ii. Insufficient sample volume 
1) An insufficient sample volume is less than 0.5 mL of plasma 
2) If between 0.25-0.5 mL: 
a)  Transfer plasma to two labeled cryovials in aliquots of equal volume 
3) If less than 0.25 mL:  
a) Transfer plasma into the cryovial labeled “AQ-1” only 
b) Mark the cryovial labeled “AQ-2” with the term “ISV”, which indicates 
“insufficient sample volume” 
c) Place the “AQ-2” cryovial labeled “ISV” in the appropriate slot in the 
“AQ-2” cryovial box inverted, so that the cap is facing downward 
rather than upward.