Cefotaxime, cephalothin, and cephapirin: antimicrobial activity and synergy studies of cephalosporins with significant in vivo desacetyl metabolite concentrations.

The desacetyl metabolites of cefotaxime, cephalothin, and cephapirin were 5-55% as active as the parent drug, depending upon the bacterial species tested. Synergy or partial synergy was demonstrated in 64% of 25 strains of Enterobacteriaceae and Staphylococcus aureus tested against cephalothin/desacetylcephalothin and cephapirin/desacetylcephapirin combinations. Some species variations were identified that influenced synergy rates, particularly among the S. aureus strains (for example, highest rates for cephapirin).