Comparative pharmacokinetics of metronidazole and tinidazole used as single dose prophylactic agents.

The pharmacokinetic properties of metronidazole (M) and tinidazole (T) were studied in patients undergoing colorectal surgery after a single preoperative dose of 1500 mg infused during 50 minutes. High-pressure liquid chromatography was used to determine serum concentrations, which for M and T were almost identical during the first 12 hours. After 24 hours, the concentration of T were slightly higher. Both drugs were detected in serum at 72 hours. The serum half-life (t1/2) was 9.4 hours for M and 17.6 hours for T, whereas the hydroxymetabolite of M had a t1/2 of 17.6 hours. There was considerable interindividual variation in both T and M concentrations. The prophylactic use of a single preoperative dose of 1500 mg of either M or T in elective colorectal surgery is supported by favourable pharmacokinetic properties of both drugs.