Disposition of cefotaxime in rat, dog and man

The excretory pathway for the elimination of 14C-cefotaxime (14C-HR 756) was found to be the same for rat, dog and man with elimination into the urine being the most important route, accounting for greater than 80% of the dosed radioactivity. The amounts of unchanged cefotaxime eliminated in the urine ranged from 20-32% in rat and dog to 56% in man. The major metabolite in each species was the microbiologically active desacetyl cefotaxime, which was present in both plasma and urine. Two further metabolites, recently identified as the stereoisomeric forms of the opened beta-lactam ring form of desacetyl cefotaxime lactone were also found in the urine of dog and man.