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warnings and cautions
5 WARNINGS AND PRECAUTIONS Peripheral neuropathy, characterized by numbness or paresthesia of an extremity has been reported in patients treated with systemic metronidazole. Although not evident in clinical trials for topical metronidazole, peripheral neuropathy has been reported with the post approval use. The appearance of abnormal neurologic signs should prompt immediate reevaluation of metronidazole gel therapy. ( 5.1 ) Metronidazole is a nitroimidazole and should be used with care in patients with evidence of, or history of, blood dyscrasia. ( 5.2 ) If dermatitis occurs, patients may need to discontinue use. ( 5.3 ) Topical metronidazole has been reported to cause tearing of the eyes. Therefore, contact with the eyes should be avoided. ( 5.4 ) 5.1 Neurologic Disease Peripheral neuropathy, characterized by numbness or paresthesia of an extremity has been reported in patients treated with systemic metronidazole. Although not evident in clinical trials for topical metronidazole, peripheral neuropathy has been reported with the post approval use. The appearance of abnormal neurologic signs should prompt immediate reevaluation of metronidazole gel therapy. Metronidazole should be administered with caution to patients with central nervous system diseases. 5.2 Blood Dyscrasias Metronidazole is a nitroimidazole; use with care in patients with evidence of, or history of, blood dyscrasia. 5.3 Contact Dermatitis Irritant and allergic contact dermatitis have been reported. If dermatitis occurs, patients may need to discontinue use. 5.4 Eye Irritation Topical metronidazole has been reported to cause tearing of the eyes. Avoid contact with the eyes.
6 ADVERSE REACTIONS Most common adverse reactions (incidence > 2%) are nasopharyngitis, upper respiratory tract infection, and headache. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact 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, 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, 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, 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 Postmarketing 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.