Urinary metabolites of 14C-labelled FCE 22101 in animals

The metabolism of 14C-FCE 22101 has been studied by radio-HPLC in the urine of various animal species. Five main chromatographic peaks were detected and named, in order of decreasing polarity, P, P1, X, UD (unchanged drug) and LP. P1 is the open beta-lactam ring metabolite obtained by the action of dehydropeptidase. The stability of FCE 22101 and P1 is pH-dependent, and differences between species in urinary metabolic patterns might therefore be partially explained by different urinary pH values.