Metabolism of cefotaxime: a review.

Cefotaxime (CTX) sodium is a potent semisynthetic cephalosporin antibiotic that has an unusually broad spectrum of antibacterial activity. This paper discusses the metabolism of 14C-CTX in rats, dogs, and humans as well as in vitro studies in cells of rats and rabbits. Excretion of radioactivity was similar in the three species, with greater than 80% of the dose being recovered in urine. About one-third of the administered dose was eliminated unchanged. Desacetylcefotaxime. (des-CTX) was the major metabolite. Ordinarily, only the two products, both having antibacterial activity, were found in plasma. Also found in dog and human urine were two other metabolites, M2 and M3, both inactive. These metabolites were, however, found in the plasma and bile of nephrectomized rats. The metabolic pathway follows the route: CTX----des-CTX----des-CTX lactone----metabolites M2 and M3. All reactions probably occur in the liver. Differences in metabolism between the species are quantitative rather than qualitative.