Metronidazole

1 INDICATIONS AND USAGE Metronidazole Gel USP, 1% is indicated for the topical treatment of inflammatory lesions of rosacea. Metronidazole Gel USP, 1% is a nitroimidazole indicated for the topical treatment of inflammatory lesions of rosacea. ( 1 )

6 ADVERSE REACTIONS Most common adverse reactions (incidence > 2%) are nasopharyngitis, upper respiratory tract infection, and headache ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Taro Pharmaceuticals U.S.A., Inc. at 1-866-923-4914 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. In a controlled clinical trial, 557 patients used metronidazole gel USP, 1% and 189 patients used the gel vehicle once daily for up to 10 weeks. The following table summarizes selected adverse reactions that occurred at a rate of ≥ 1%: Table 1: Adverse Reactions That Occurred at a Rate of ≥1% System Organ Class/Preferred Term Metronidazole Gel USP, 1% Gel Vehicle N=557 N=189 Patients with at least one AE Number (%) of Patients 186 (33.4) 51 (27.0) Infections and infestations 76 (13.6) 28 (14.8) Bronchitis 6 (1.1) 3 (1.6) Influenza 8 (1.4) 1 (0.5) Nasopharyngitis 17 (3.1) 8 (4.2) Sinusitis 8 (1.4) 3 (1.6) Upper respiratory tract infection 14 (2.5) 4 (2.1) Urinary tract infection 6 (1.1) 1 (0.5) Vaginal mycosis 1 (0.2) 2 (1.1) Musculoskeletal and connective tissue disorders 19 (3.4) 5 (2.6) Back pain 3 (0.5) 2 (1.1) Neoplasms 4 (0.7) 2 (1.1) Basal cell carcinoma 1 (0.2) 2 (1.1) Nervous system disorders 18 (3.2) 3 (1.6) Headache 12 (2.2) 1 (0.5) Respiratory, thoracic and mediastinal disorders 22 (3.9) 5 (2.6) Nasal congestion 6 (1.1) 3 (1.6) Skin and subcutaneous tissue disorders 36 (6.5) 12 (6.3) Contact dermatitis 7 (1.3) 1 (0.5) Dry skin 6 (1.1) 3 (1.6) Vascular disorders 8 (1.4) 1 (0.5) Hypertension 6 (1.1) 1 (0.5) Table 2: Local Cutaneous Signs and Symptoms of Irritation That Were Worse Than Baseline Metronidazole Gel USP, 1% Gel Vehicle Sign/Symptom N=544 N=184 Dryness 138 (25.4) 63 (34.2) Mild 93 (17.1) 41 (22.3) Moderate 42 (7.7) 20 (10.9) Severe 3 (0.6) 2 (1.1) Scaling 134 (24.6) 60 (32.6) Mild 88 (16.2) 32 (17.4) Moderate 43 (7.9) 27 (14.7) Severe 3 (0.6) 1 (0.5) Pruritus 86 (15.8) 35 (19.0) Mild 53 (9.7) 21 (11.4) Moderate 27 (5.0) 13 (7.1) Severe 6 (1.1) 1 (0.5) Stinging/burning 56 (10.3) 28 (15.2) Mild 39 (7.2) 18 (9.8) Moderate 7 (1.3) 9 (4.9) Severe 10 (1.8) 1 (0.5) The following additional adverse experiences have been reported with the topical use of metronidazole: skin irritation, transient redness, metallic taste, tingling or numbness of extremities, and nausea. 6.2 Post Marketing Experience The following adverse reaction has been identified during post approval use of topical metronidazole: peripheral neuropathy. Because this reaction is reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate the frequency or establish a causal relationship to drug exposure.

4 CONTRAINDICATIONS Metronidazole Gel USP, 1% is contraindicated in patients with a history of hypersensitivity to metronidazole or to any other ingredient in the formulation. Metronidazole Gel USP, 1% is contraindicated in those patients with a history of hypersensitivity to metronidazole or to any other ingredient in this formulation. ( 4 )

11 DESCRIPTION Metronidazole Gel USP, 1% contains metronidazole, USP. Chemically, metronidazole is 2-methyl-5-nitro-1 H -imidazole- 1-ethanol. The molecular formula for metronidazole is C 6 H 9 N 3 O 3 . It has the following structural formula: Metronidazole has a molecular weight of 171.16. It is a white to pale yellow crystalline powder. It is slightly soluble in alcohol and has solubility in water of 10 mg/mL at 20°C. Metronidazole belongs to the nitroimidazole class of compounds. Metronidazole is a colorless to slightly yellow gel; each gram contains 10 mg of metronidazole in a base of alcohol (10% w/w), disodium edetate, hydroxyethylcellulose, methylparaben, polyethylene glycol, propylene glycol, propylparaben, and purified water. Chemical Structure

2 DOSAGE AND ADMINISTRATION Apply and rub in a thin film of metronidazole once daily to affected area(s). A gentle cleanser should be used before the application of metronidazole. Cosmetics may be applied after the application of metronidazole. Not for oral, ophthalmic or intravaginal use. Not for oral, ophthalmic or intravaginal use. Apply and rub in a thin film of metronidazole once daily to affected area(s). ( 2 ) Treated areas should be cleansed before the application of metronidazole. ( 2 ) Cosmetics may be applied after the application of metronidazole. ( 2 )

10 OVERDOSAGE There are no reported human experiences with overdosage of metronidazole. Topically applied metronidazole can be absorbed in sufficient amount to produce systemic effects.

7 DRUG INTERACTIONS Oral metronidazole has been reported to potentiate the anticoagulant effect of coumarin and warfarin, resulting in a prolongation of prothrombin time. Drug interactions should be kept in mind when metronidazole is prescribed for patients who are receiving anticoagulant treatment, although they are less likely to occur with topical metronidazole administration because of low absorption. Oral metronidazole has been reported to potentiate the anticoagulant effect of coumarin and warfarin, resulting in a prolongation of prothrombin time. Drug interactions should be kept in mind when metronidazole is prescribed for patients who are receiving anticoagulant treatment, although they are less likely to occur with topical metronidazole administration because of low absorption. ( 7 )

12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action The mechanism of action of metronidazole in the treatment of rosacea is unknown. 12.2 Pharmacodynamics The pharmacodynamics of metronidazole in association with the treatment of rosacea are unknown. 12.3 Pharmacokinetics Topical administration of a one gram dose of metronidazole to the face of 13 patients with moderate to severe rosacea once daily for 7 days resulted in a mean ± SD C max of metronidazole of 32 ± 9 ng/mL. The mean ± SD AUC (0-24) was 595 ± 154 ng*hr/mL. The mean C max and AUC (0-24) are less than 1% of the value reported for a single 250 mg oral dose of metronidazole. The time to maximum plasma concentration (T max ) was 6 to 10 hours after topical application.

12.1 Mechanism of Action The mechanism of action of metronidazole in the treatment of rosacea is unknown.

12.2 Pharmacodynamics The pharmacodynamics of metronidazole in association with the treatment of rosacea are unknown.

12.3 Pharmacokinetics Topical administration of a one gram dose of metronidazole to the face of 13 patients with moderate to severe rosacea once daily for 7 days resulted in a mean ± SD C max of metronidazole of 32 ± 9 ng/mL. The mean ± SD AUC (0-24) was 595 ± 154 ng*hr/mL. The mean C max and AUC (0-24) are less than 1% of the value reported for a single 250 mg oral dose of metronidazole. The time to maximum plasma concentration (T max ) was 6 to 10 hours after topical application.

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3 DOSAGE FORMS AND STRENGTHS Gel, 1%. Metronidazole is a colorless to slightly yellow gel. Each gram of metronidazole contains 10 mg (1%) of metronidazole. Gel, 1%.

Metronidazole Metronidazole Metronidazole Metronidazole alcohol edetate disodium methylparaben polyethylene glycol, unspecified propylparaben propylene glycol water clear to yellow

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility Metronidazole has shown evidence of carcinogenic activity in a number of studies involving chronic, oral administration in mice and rats, but not in studies involving hamsters. In several long-term studies in mice, oral doses of approximately 225 mg/m 2 /day or greater (approximately 37 times the human topical dose on a mg/m 2 basis) were associated with an increase in pulmonary tumors and lymphomas. Several long-term oral studies in the rat have shown statistically significant increases in mammary and hepatic tumors at doses >885 mg/m 2 /day (144 times the human dose). Metronidazole has shown evidence of mutagenic activity in several in vitro bacterial assay systems. In addition, a dose-related increase in the frequency of micronuclei was observed in mice after intraperitoneal injections. An increase in chromosomal aberrations in peripheral blood lymphocytes was reported in patients with Crohn's disease who were treated with 200 to 1200 mg/day of metronidazole for 1 to 24 months. However, in another study, no increase in chromosomal aberrations in circulating lymphocytes was observed in patients with Crohn's disease treated with the drug for 8 months. In one published study, using albino hairless mice, intraperitoneal administration of metronidazole at a dose of 45 mg/m 2 /day (approximately 7 times the human topical dose on a mg/m 2 basis) was associated with an increase in ultraviolet radiation induced skin carcinogenesis. Neither dermal carcinogenicity nor photocarcinogenicity studies have been performed with metronidazole gel USP, 1% or any marketed metronidazole formulations.

13 NONCLINICAL TOXICOLOGY 13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility Metronidazole has shown evidence of carcinogenic activity in a number of studies involving chronic, oral administration in mice and rats, but not in studies involving hamsters. In several long-term studies in mice, oral doses of approximately 225 mg/m 2 /day or greater (approximately 37 times the human topical dose on a mg/m 2 basis) were associated with an increase in pulmonary tumors and lymphomas. Several long-term oral studies in the rat have shown statistically significant increases in mammary and hepatic tumors at doses >885 mg/m 2 /day (144 times the human dose). Metronidazole has shown evidence of mutagenic activity in several in vitro bacterial assay systems. In addition, a dose-related increase in the frequency of micronuclei was observed in mice after intraperitoneal injections. An increase in chromosomal aberrations in peripheral blood lymphocytes was reported in patients with Crohn's disease who were treated with 200 to 1200 mg/day of metronidazole for 1 to 24 months. However, in another study, no increase in chromosomal aberrations in circulating lymphocytes was observed in patients with Crohn's disease treated with the drug for 8 months. In one published study, using albino hairless mice, intraperitoneal administration of metronidazole at a dose of 45 mg/m 2 /day (approximately 7 times the human topical dose on a mg/m 2 basis) was associated with an increase in ultraviolet radiation induced skin carcinogenesis. Neither dermal carcinogenicity nor photocarcinogenicity studies have been performed with metronidazole gel USP, 1% or any marketed metronidazole formulations.

ANDA204651

Metronidazole

Metronidazole

51672-4164

HUMAN PRESCRIPTION DRUG

TOPICAL

PRINCIPAL DISPLAY PANEL - 45 g Tube Carton NDC 51672-4164-6 45 g Metronidazole Gel USP, 1% FOR TOPICAL USE ONLY. NOT FOR ORAL, OPHTHALMIC OR INTRAVAGINAL USE. Rx only Keep this and all medications out of the reach of children. TARO PRINCIPAL DISPLAY PANEL - 45 g Tube Carton

Rx Only Mfd. by: Taro Pharmaceutical Industries Ltd. Haifa Bay, Israel 2624761 Dist. by: Taro Pharmaceuticals U.S.A., Inc. Hawthorne, NY 10532 Revised: November 2018 20419-1118-2 782

17 PATIENT COUNSELING INFORMATION Patients using Metronidazole Gel USP, 1% should receive the following information and instructions: This medication is to be used as directed. It is for external use only. Avoid contact with the eyes. Cleanse affected area(s) before applying Metronidazole Gel USP, 1%. This medication should not be used for any condition other than that for which it is prescribed. Keep out of reach of children. Patients should report any adverse reaction to their physicians.

14 CLINICAL STUDIES In a randomized, vehicle-controlled trial, 746 subjects with rosacea were treated with metronidazole gel USP, 1% or gel vehicle once daily for 10 weeks. Most subjects had "moderate" rosacea at baseline. Efficacy was determined by recording reduction in inflammatory lesion counts and success rate in the Investigator Global Assessment (percentage of subjects "clear" and "almost clear" of rosacea at the end of the study). The scale is based on the following definitions: Table 3: Investigator Global Assessment Scale Score Grade Definition 0 Clear No signs or symptoms present; at most, mild erythema 1 Almost Clear Very mild erythema present. Very few small papules/pustules 2 Mild Mild erythema. Several small papules/pustules 3 Moderate Moderate erythema. Several small or large papules/pustules, and up to 2 nodules 4 Severe Severe erythema. Numerous small and/or large papules/pustules, up to several nodules The results are shown in the following table: Table 4: Inflammatory Lesion Counts and Global Scores in a Clinical Trial of Rosacea Metronidazole Gel USP, 1% Vehicle N Results N (%) N Results N (%) Inflammatory lesions 557 189 Baseline, mean count 18.3 18.4 Week-10, mean count 8.9 12.8 Reduction 9.4 (50.7) 5.6 (32.6) Investigator Global Assessment 557 189 Subject clear or almost clear 214 (38.42) 52 (27.51) Subject with no change 159 (28.5) 77 (40.7) Subjects treated with metronidazole gel USP, 1% experienced a mean reduction of 9.4 inflammatory lesions in the Week-10 LOCF group, compared to a reduction of 5.6 for those treated with vehicle, or a difference in means of 3.8 lesions. The contribution to efficacy of individual components of the vehicle has not been established.

8.5 Geriatric Use Sixty-six subjects aged 65 years and older were treated with metronidazole gel USP, 1% in the clinical study. No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

8.3 Nursing Mothers After oral administration, metronidazole is secreted in breast milk in concentrations similar to those found in the plasma. Even though blood levels taken after topical metronidazole application are significantly lower than those achieved after oral metronidazole a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother and the risk to the infant.

8.4 Pediatric Use Safety and effectiveness in pediatric patients have not been established.

8.1 Pregnancy Teratogenic Effects: Pregnancy Category B. There are no adequate and well-controlled studies with the use of metronidazole in pregnant women. Metronidazole crosses the placental barrier and enters the fetal circulation rapidly. No fetotoxicity was observed after oral administration of metronidazole in rats or mice at 200 and 20 times, respectively, the expected clinical dose. However, oral metronidazole has shown carcinogenic activity in rodents. Because animal reproduction studies are not always predictive of human response, metronidazole should be used during pregnancy only if clearly needed.

Teratogenic Effects: Pregnancy Category B. There are no adequate and well-controlled studies with the use of metronidazole in pregnant women. Metronidazole crosses the placental barrier and enters the fetal circulation rapidly. No fetotoxicity was observed after oral administration of metronidazole in rats or mice at 200 and 20 times, respectively, the expected clinical dose. However, oral metronidazole has shown carcinogenic activity in rodents. Because animal reproduction studies are not always predictive of human response, metronidazole should be used during pregnancy only if clearly needed.

8 USE IN SPECIFIC POPULATIONS 8.1 Pregnancy Teratogenic Effects: Pregnancy Category B. There are no adequate and well-controlled studies with the use of metronidazole in pregnant women. Metronidazole crosses the placental barrier and enters the fetal circulation rapidly. No fetotoxicity was observed after oral administration of metronidazole in rats or mice at 200 and 20 times, respectively, the expected clinical dose. However, oral metronidazole has shown carcinogenic activity in rodents. Because animal reproduction studies are not always predictive of human response, metronidazole should be used during pregnancy only if clearly needed. 8.3 Nursing Mothers After oral administration, metronidazole is secreted in breast milk in concentrations similar to those found in the plasma. Even though blood levels taken after topical metronidazole application are significantly lower than those achieved after oral metronidazole a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother and the risk to the infant. 8.4 Pediatric Use Safety and effectiveness in pediatric patients have not been established. 8.5 Geriatric Use Sixty-six subjects aged 65 years and older were treated with metronidazole gel USP, 1% in the clinical study. No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

16 HOW SUPPLIED/STORAGE AND HANDLING Metronidazole Gel USP, 1% is colorless to slightly yellow in color, and supplied as follows: 45 g tube - (NDC 51672-4164-6) 60 g tube - (NDC 51672-4164-3) 55 g pump - (NDC 51672-4164-9) Storage Conditions: Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].

Storage Conditions: Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].