Biological availability and pharmacokinetics of tinidazole after single and repeated doses

Tinidazole was administered to healthy volunteers and serum concentrations were measured following single oral and intravenous doses and after repeated dosage at different dose levels. The elimination half-time was 12-13 h. Pharmacokinetics did not change with dose, route of administration or repeated dosage. The bioavailability of single oral doses ranged between 88 and 129% with a mean of 99%. Serum concentration curves tended to have double peaks or plateaus at about 4-6 h. 74% of the intravenous dose was eliminated from serum at 24 h, but only 19% was recovered in the urine, suggesting alternative ways of elimination. Excretion in the bile and a subsequent enterohepatic circulation may explain the variations in bioavailability and the shape of the serum concentration curves.