Absorption, distribution, excretion and metabolism of cefmetazole in cynomolgus monkeys

The pharmacokinetics and metabolic fate of cefmetazole (CS-1170, CMZ) were studied in cynomolgus monkeys by means of combination of radio- and bioassay techniques and that of three radioactive drugs labeled at the different moiety of the molecule. The plasma level of radioactivity after intramuscular injection of cefmetazole[methoxyl-14C] (50 mg/kg) reached the maximum level (185 microgram/ml) after 10 minutes and declined with a half-life of about 48 minutes. In the thin-layer chromatography of the plasma extracts, a single radioactive spot was detected corresponding to unchanged cefmetazole. Repeated intravenous administration for one and two weeks showed no effect on the plasma levels and half-lives. More than 75% of the intravenous or intramuscular dose was recovered in the urine by both radio- and bioassay, the most part being excreted during the first 3 hours period. On the TLC of urine, 93--97% was detected as unchanged cefmetazole. In the bile, the most part (less than 80%) was detected as unchanged cefmetazole. In the feces, about 15% of the dose was recovered, in which 30--40% was detected as intact cefmetazole. The metabolic fate of [3-35S] and [7-35S]cefmetazole was described and discussed. The whole-body autoradiography in the monkeys was also presented.