DESCRIPTION
MetroGel® Topical Gel contains metronidazole, USP, at a concentration of 7.5 mg per gram (0.75%) in a gel consisting of purified water, methylparaben, propylparaben, propylene glycol, carbomer 940, sodium hydroxide, and edetate disodium. Metronidazole is classified therapeutically as an antiprotozoal and antibacterial agent. Chemically, metronidazole is named 2-methyl-5-nitro-1 H - imidazole-1-ethanol and has the following structure:
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CLINICAL PHARMACOLOGY
Bioavailability studies on the topical administration of 1 gram of MetroGel® Topical Gel (7.5 mg of metronidazole) to the face of 10 rosacea patients showed a maximum serum concentration of 66 nanograms per milliliter in one patient. This concentration is approximately 100 times less than concentrations afforded by a single 250 mg oral tablet. The serum metronidazole concentrations were below the detectable limits of the assay at the majority of time points in all patients. Three of the patients had no detectable serum concentrations of metronidazole at any time point. The mean dose of gel applied during clinical studies was 600 mg which represents 4.5 mg of metronidazole per application. Therefore, under normal usage levels, the formulation affords minimal serum concentrations of metronidazole. The mechanisms by which MetroGel® (metronidazole topical gel) Topical Gel acts in the treatment of rosacea are unknown, but appear to include an anti-inflammatory effect.
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