Mutagenicity of metronidazole: presence of several active metabolites in human urine.

Mutagenic activity was found in the urine of 10 patients given therapeutic dosages of metronidazole orally or per vagina. Paper chromatographic separation revealed that mutagenicity in the urine was associated with unmodified metronidazole and at least four of its known urinary metabolites. Activity was also recovered in a region of the chromatogram heretofore not assigned to a metronidazole metabolite.