Metabolism of cefotaxime in animals and man

The metabolism of cefotaxime in rat, dog and man has been studied. In all species the compound is well absorbed following intramuscular administration, and elim-inated mainly via the urine. The amount of unchanged cefotaxime eliminated in the urine is similar for each species with the major metabolite being desacetyl cefotaxime. Two further metabolites, UP1 and UP2, are detected in dog and human urine but not rat urine. UP1 and UP2 were observed in the bile of nephrectomized rats. Studies have shown that the metabolic pathway follows the route: cefotaxime-»des-acetyl cefotaxime->desacetyl cefotaxime lactone->UP metabolites. These conver-sions probably occur in the liver. The structure of the UP metabolites has been elucidated. Finally it is suggested that the species differences observed are- more quantitative than qualitative and that the formation of the UP metabolites is related to the rate of renal elimination of desacetyl cefotaxime