Evaluation of the Bioavailability of Metronidazole Dermal Products
Phase: EARLY_PHASE1
Conditions: Bioequivalence
Sponsor: University of Maryland, Baltimore

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
1 
EVALUATION OF THE BIOAVAILABILITY OF METRONIDAZOLE DERMAL 
PRODUCTS 
 
Short title: PK of metronidazole dermal products 
UMB IRB #:  HP-00071790 
 
Principal Investigators:  
Audra L. Stinchcomb (contact), PhD, RPh (PI) 
 
Medically Accountable Investigators: 
Jeffrey Fink, MD, MS (primary) 
Lee-Ann Wagner, MD (secondary) 
 
Sponsor: 
Food and Drug Administration 
Office of Generic Drugs 
 
Grant Number: 1U01FD004947  
NCT:  NCT03271983 
Version 7.0 
12 April 2019 
 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
2 
STATEMENT OF COMPLIANCE 
This trial will be conducted in compliance with the protocol, International Conference on 
Harmonization Good Clinical Practice E6 (ICH-GCP) and the applicable Food and Drug 
Administration and other Department of Health and Human Services regulatory requirements. 
All key personnel (all individuals responsible for the design and conduct of this study) have 
completed Human Subjects Protection Training. 
 
 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
3 
PROTOCOL SUMMARY 
Title:  
Evaluation of the bioavailability of metronidazole dermal 
products 
Population: 
Healthy adults age 18 - 45 years 
Number of Sites: 
Single site: University of Maryland School of Medicine 
Study Duration: 
Approximately up to 1 year 
 
Subject Participation 
Duration: 
Approximately 10 weeks including the screening period 
 
Description of Study 
Product: 
Metronidazole 
topical 
gel, 
0.75%, 
Prasco 
Laboratories; 
Metronidazole 
topical 
gel, 
0.75%, 
Impax 
Laboratories; 
Metronidazole topical cream, 0.75%, Fougera Laboratories. 
 
Objective: 
 
 
The present study aims to study the systemic bioavailability of 
metronidazole in healthy volunteers following the application of 
topical metronidazole products: metronidazole topical gel, 
0.75% (RLD), metronidazole topical gel, 0.75% (generic) and 
metronidazole 
topical 
cream, 
0.75% 
(generic). 
The 
metronidazole 
gel, 
0.75% 
products 
are 
therapeutically 
equivalent. The metronidazole cream, 0.75% will be used as an 
inequivalent control for the study. 
The pharmacokinetic data obtained in this study will be used in 
combination with in vitro data collected elsewhere to develop an 
in vitro in vivo correlation that could be leveraged to evaluate 
bioequivalence of generic metronidazole topical drug products.  
Description of Study 
Design: 
The study will be an open-label, crossover study over 10 weeks 
(n=12 healthy subjects) with one week washout period between 
studies. 
The study contain six procedure days: 
• 
Procedure Day 1:  RLD topical gel containing 0.75% 
metronidazole to be applied for 25 h.  Blood samples 
obtained on Procedure Day 1 and 2. 
• 
Procedure Day 3: Generic topical gel containing 0.75% 
metronidazole to be applied for 25 h.  Blood samples 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
4 
obtained on Procedure Day 3 and 4. 
• 
Procedure Day 5:  Generic topical cream containing 0.75% 
metronidazole to be applied for 25 h.  Blood samples 
obtained on Procedure Day 5 and 6. 
A)  Pharmacokinetics 
Each subject will be his/her own control and each subject will 
sign an institutional review board–approved consent form 
explaining the purpose, nature, risks, benefits, and duration of 
the study. The study will be conducted in accordance with good 
clinical practice guidelines and with the ethical principles 
originating in the Declaration of Helsinki.  
The subject’s skin in the area of application (upper arm) will be 
relatively free of hair before gel or cream application.  Blood 
samples (approximately 5 mL (1 tsp) each) will be drawn in BD 
vacutainer tubes.  On Procedure Day 1, 2, 3, 4, 5 and 6, blood 
samples will be obtained as follows: 
• 
Within 60 min pre-gel/cream application and then during 
wear, up to 25 h.   
 
 
 
 
 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
5 
1 KEY ROLES 
U01 Principal Investigators: 
 
 
Audra L. Stinchcomb (contact), PhD, RPh (PI) 
Professor 
Department of Pharmaceutical Sciences 
University of Maryland School of Pharmacy 
20 N Pine St, Room PHN521 
Baltimore, MD 21201 
Phone: 410-706-2646 
Fax: 410-706-0886 
Email: astinchc@rx.umaryland.edu  
 
 
 
 
Medically Accountable 
Investigators 
 
 
Jeffrey C Fink MD, MS (primary) 
Professor 
Department of Medicine and Epidemiology (secondary) 
University of Maryland School of Medicine 
UMMC, Room NN3E03 
Baltimore, MD 21201 
Phone: 410-328-4822 
Fax: 410-328-5685 
 
E-mail: jfink@medicine.umaryland.edu 
 
 
Lee-Ann Wagner, M.D. (secondary) 
University of Maryland School of Medicine 
Department of Medicine  
Pediatrics 
North Hospital 
Baltimore, MD 21201 
Phone: 410-328-7605 or 410-328-3158 
Email :  lwagner@som.umaryland.edu 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
12 
Schematic of Study Design 
n=12 subjects 
 
Study Session 1  
[Procedure Day 1 and 2] 
Product: 
Metronidazole  gel, 0.75% (RLD) 
Time of admission: 
Time of application: 
Morning of Procedure Day 1  
Morning of Procedure Day 1  
Duration of application: 
25 h 
Sampling: 
26 hours 
 
 
  Sampling time points: 
-60 min, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 23, 24, 25 h   
 
 
 
 
 
Washout period at least 1 week 
 
Study Session 2 
[Procedure Day 3 and 4] 
Product: 
Metronidazole gel, 0.75% (generic) 
Time of admission: 
Time of application: 
Morning of Procedure Day 3  
Morning of Procedure Day 3  
Duration of application: 
25 h 
Sampling: 
Sampling time points: 
26 hours 
-60 min, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 23, 24, 25 h   
 
 
   
Washout period at least 1 week 
 
Study Session 3 
[Procedure Day 5 and 6] 
Product: 
Metronidazole cream, 0.75% (generic)  
Time of admission: 
Time of application: 
Morning of Procedure Day 5  
Morning of Procedure Day 5  
Duration of application: 
25 h 
Sampling: 
Sampling time points: 
26 hours 
-60 min, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 23, 24, 25 h   
 
 
   
 
 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
13 
2 BACKGROUND INFORMATION AND SCIENTIFIC 
RATIONALE 
2.1 
Background Information 
Generic drugs are approved based upon bioequivalence (BE) testing, and with respect 
to oral drug delivery, the accepted BE approach is relatively straightforward and is 
principally based on matching blood level profiles. In some cases, in vitro dissolution 
tests can be done to help determine the bioequivalence of an oral dosage form.  For 
topical drug products in the United States, with the exception of corticosteroids and a 
few other products, a comparative clinical endpoint study is often necessary for approval 
of a generic product or for replacement of an approved dermatological drug product with 
one that has major changes. Comparative clinical trials are relatively insensitive, time-
consuming and costly.  It is especially difficult to gain the adequate statistical power 
needed to evaluate bioequivalence for some dermatological conditions, and can require 
a large number (i.e., hundreds1,2) of subjects. 
This study supports FDA’s continuing effort to identify the most accurate, sensitive, 
reproducible and efficient methods to evaluate topical dermatological drug products.  
The model drug for this study is metronidazole, which is available in different topical 
formulations, gel, cream and lotion, approved by the United States FDA. The 
metronidazole gels and cream have been chosen for this study because the 
therapeutically equivalent metronidazole gels will be used to evaluate BE in vivo. The 
metronidazole cream is being used as the non-BE control for this project.  
   
2.2 
Rationale 
The goal of this study is to help establish more efficient pathways for approval of topical 
drug products by developing better tools to assess bioavailability. This study with a RLD 
and generic metronidazole topical gel, 0.75% and generic metronidazole topical cream, 
0.75% will provide sufficient systemic concentrations of metronidazole to characterize the 
systemic bioavailability. The same products will also be studied (under a parallel but 
separate in vitro study protocol) using an in vitro permeation test (IVPT) model with 
excised human skin. The IVPT model has demonstrated IVIVC in previous studies using 
different drug molecules and formulations. This research will help establish whether the 
IVPT model correlates with and is predictive of in vivo bioavailability, and whether IVPT 
can be utilized as part of a collective weight-of-evidence approach to support an approval 
pathway for topical drug products. 
 
These coordinated evaluations also collectively provide the in vivo reference datasets 
that are needed to establish IVIVC for the IVPT model which may then be utilized to 
support a new pathway for approval of numerous topical drug products for patients. 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
14 
Metronidazole topical products 
  
Metronidazole  
 gel, 0.75% (RLD) 
NDC: 66993-962-45 
Metronidazole  
gel, 0.75% (generic) 
NDC: 0115-1474-46 
Metronidazole cream, 
0.75% (generic) 
NDC: 0168-0323-46 
Inactive 
ingredients 
0.8 mg of methylparaben 
and 0.2 mg of 
propylparaben as 
preservatives in a gel 
consisting of carbomer 
940, edetate disodium, 
propylene glycol, purified 
water and sodium 
hydroxide 
Carbopol 980, edetate 
disodium, 
methylparaben, 
propylene glycol, 
propylparaben, purified 
water and sodium 
hydroxide 
Emulsifying wax, 
sorbitol solution, 
glycerin, isopropyl 
palmitate, benzyl 
alcohol, lactic acid, 
sodium hydroxide and 
purified water 
  
 
 
Formulation 
topical gel 
topical gel 
topical cream 
  
  
 
 
Manufacturer 
Prasco Laboratories 
Impax Generics 
Fougera Laboratories 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
15 
3 OBJECTIVES 
3.1 
Study Objectives 
1)  Generate human PK data by collecting data following the application of three 
metronidazole formulations:  RLD and generic metronidazole gel, 0.75% and generic 
metronidazole cream, 0.75%. This data will be used to assess the bioequivalence of 
these products or lack thereof.   
2)  To develop in vitro/in vivo correlation (IVIVC) models for dermal products. PK data 
from this study as well as in vitro data collected elsewhere from IVPT studies will be 
used to develop IVIVC models which could provide a surrogate for conducting clinical 
endpoint studies (required to demonstrate bioequivalence of dermal products).  
3.2 
Study Outcome Measures 
For the PK study the main outcome measure is the maximum serum concentration 
(Cmax), time of maximum serum concentration (Tmax) of metronidazole and area under the 
curve (AUC) attained from RLD and generic metronidazole gel, 0.75% and generic 
metronidazole cream, 0.75%.       
 
 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
16 
4   STUDY ENROLLMENT AND WITHDRAWAL 
4.1 
Subject Inclusion Criteria 
Subjects are eligible for this study if they fulfill the inclusion criteria specified below: 
1. Men or non-pregnant, women who are of any ethnic background between the 
age of 18 and 45 years old. 
2. Subjects must be non-smokers/tobacco users (must have refrained from the use 
of nicotine-containing substances (e.g., cigarettes, cigars, chewing tobacco, 
snuff, gum, patches or electronic cigarettes) over the previous 2 months and are 
not currently smoking/using tobacco products. 
3. Provide written informed consent before initiation of any of the study procedures. 
4. Agree not to participate in another clinical trial/study during the study period or to 
participate in an investigational drug study for at least 1 month after the last study 
session.   
5. Able to adhere to the study protocol schedule and study restrictions.   
6. Able to participate in all study sessions. 
7. Subjects have upper arms large enough to allow for the placement of 200 cm2 
[31 in2] area for application of gels or cream. 
8. Subjects deemed to be healthy as judged by the Medically Accountable 
Investigator (MAI) and determined by medical history, physical examination and 
medication history. 
9. Negative urine drug screening test (cannabinoids, amphetamines, barbiturates, 
benzodiazepine, cocaine, methadone, opiates, PCP). 
10. Have normal screening laboratories for WBC, Hgb, platelets, sodium, potassium, 
chloride, bicarbonate, BUN, creatinine, ALT and AST. 
11. Have normal screening laboratories for urine protein and urine glucose.  
12. Female subjects must be of non-childbearing potential (as defined as surgically 
sterile [i.e. history of hysterectomy or tubal ligation] or postmenopausal for more 
than 1 year), or if of childbearing potential must be non-pregnant at the time of 
enrollment and on the morning of each procedure day, and must agree to use 
reliable hormonal or barrier birth control such as implants, injectables, combined 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
17 
oral contraceptives, some intrauterine devices (IUDs), sexual abstinence, or a 
vasectomized partner.  
13. Agrees not to donate blood to a blood bank throughout participation in the study 
and at least 3 months after the last study session. 
14. Have a normal ECG; must not have the following to be acceptable: pathologic Q 
wave abnormalities, significant ST–T wave changes, left ventricular hypertrophy, 
right bundle branch block, left bundle branch block. (sinus rhythm is between 55–
100 beats per minute). 
15. Have normal vital signs: 
• Temperature 35-37.9°C (95-100.3°F) 
• Systolic blood pressure 90-165 mmHg 
• Diastolic blood pressure 60-100 mmHg 
• Heart rate 55-100 beats per minute 
• Respiration rate 12-20 breaths per minute 
4.2 
Subject Exclusion Criteria 
Subjects will be excluded for any of the following conditions/reasons: 
1. Women who are pregnant, lactating, breast feeding or have a positive serum 
pregnancy test at enrollment or positive urine pregnancy test on the morning of 
each study session. 
2. Smokers/tobacco users (current use or use over the previous 2 months of 
nicotine-containing substances (e.g., cigarettes, cigars, chewing tobacco, snuff, 
gum, patch or electronic cigarettes). 
3. Participation in any ongoing investigational drug trial/study or clinical drug 
trial/study. 
4. History as either reported by the subject or evident to the Medically Accountable 
Investigator (MAI) of infectious disease or skin infection or of chronic skin 
disease (e.g., psoriasis, atopic dermatitis). 
5. History of diabetes. 
6. History of significant dermatologic cancers (e.g., melanoma, squamous cell 
carcinoma), except basal cell carcinomas that were superficial and did not 
involve the investigative site. 
7. Body Mass Index (BMI) ≥30 kg/m2. 
8. History of chronic obstructive pulmonary disease or cor pulmonale, or 
substantially decreased respiratory reserve, hypoxia, hypercapnia or pre-existing 
respiratory depression. 
9. Active positive Hepatitis B, C and/or HIV serologies (see Appendix B). 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
18 
10. Positive urine drug screening test. 
11. Use of chronic prescription medications during the period 0 to 30 days; or over-
the counter medications (e.g. antihistamines, topical corticosteroids) and short 
term (<30 days) prescription medications during the period 0-3 days before a 
study session (vitamin, herbal supplements and birth control medications not 
included). 
12. Currently taking daily anticoagulants (warfarin, heparin, rivaroxaban, dabigatran, 
etc…) within the past month prior to entry into the study. 
13. Have Crohn’s disease. 
14. History of blood dyscrasia. 
15. Donation or loss of greater than one pint of blood within 60 days of entry to the 
study. 
16. Any prior adverse reaction or hypersensitivity to metronidazole, parabens, other 
inactive ingredients in the gels or cream or to medical tape products.  
17. Received an experimental agent (vaccine, drug, biologic, device, blood product 
or medication) within 1 month before enrollment in this study or expects to 
receive an experimental agent during the study. 
18. Consumption (food or drink) of alcohol within 48 hours prior to dose 
administration. 
19. Any condition that would, in the opinion of the Medically Accountable Investigator 
(MAI), place the subject at an unacceptable risk of injury or render the subject 
unable to meet the requirements of the protocol. 
20. Subject has an obvious difference in skin color between arms or the presence of 
a skin condition, excessive hair at the application site (upper arms), sunburn, 
raised moles and scars, open sores at application site (upper arms), scar tissue, 
tattoo, or coloration that would interfere with placement of metronidazole 
products, skin assessment, or reactions to metronidazole. 
 
 

PK of Metronidazole Dermal Products 
Version 7.0; April 12, 2019 
 ____________________________________________________________________________________________ 
 ____________________________________________________________________________________________ 
19 
5 
PHARMACOKINETICS AND STATISTICAL 
CONSIDERATIONS 
5.1 
Analyses 
Metronidazole concentrations will be measured in serum samples collected from each 
subject. Blood samples (approximately 5 mL (1 tsp)) will be collected during each study 
session within -60 min prior to gel or cream application and then at 1 h, 2 h, 3 h, 4 h, 5 h, 
6 h, 7 h, 8 h, 9 h, 10 h, 23 h, 24 h and 25 h post-application. Non compartmental 
analyses (NCA) will be conducted to estimate the PK parameters such as: maximum 
serum concentration (Cmax) and AUC of the serum concentration–time determined by the 
linear trapezoidal method. All NCA analyses will be conducted using Phoenix® 
WinNonlin® 6.4 (Pharsight, a Certara Company, CA). 
5.2 
Final Analysis Plan 
The objective of this study is to determine PK parameters (Cmax, AUC) of metronidazole 
in healthy adults after using metronidazole 0.75% gels or cream.  
Student’s t-test or Analysis of variance (ANOVA) followed by post-hoc Bonferroni test 
will be used, where appropriate, for comparing the differences in the means of the PK 
parameters and significant differences will be declared at p<0.05.  
 
If metronidazole PK concentrations are found to be non-normally distributed, then we will 
examine Box-Cox transformations (e.g., log, square-root, etc.) that can achieve 
normality. If no transformation can achieve normality, then will use permutation tests to 
compute empirical p-values, and will use the bootstrap to compute standard errors and 
confidence intervals that account for within-person correlation.