Serum levels and urinary excretion of parent antibiotics and desacetyl forms after parenteral administration of cephalothin and cephapirin.

When the antibacterial substances of cephalothin and cephapirin in the serum and urine after intramuscular injection were separated and assayed, desacetyl metabolities of both drugs were detected. These tendencies were especially apparent in the tissue concentrations. When both the drugs were given intravenously to healthy volunteers, the amounts of their desacetyl metabolites were not greater in man than in rats.