Pharmacokinetics of tinidazole and metronidazole in women after single large oral doses

Abstract

Serum concentrations of tinidazole and metronidazole have been measured in healthy female volunteers who received a single dose of 2 g. of each drug in a cross over study. Bioassays against T. vaginalis showed that metronidazole achieved higher peak concentrations (mean 81 μg./ml.) than did tinidazole (mean 67 μg./ml.), while assays for unchanged drug showed higher peak concentrations of tinidazole (mean 51 μg./ml.) than of metronidazole (mean 40 μg./ml.). This discrepancy is probably due to the presence in the serum of active metabolites of metronidazole. The longer half life of tinidazole led to significantly higher serum concentrations (by bioassay and chemical assay) of tinidazole than of metronidazole from 6 hrs onwards.