Ceftizoxime suppository (CZX-S) was administered rectally to mice, rats and dogs, and the pharmacokinetics were studied in comparison with those after intravenous, intramuscular and subcutaneous administration of ceftizoxime (CZX). Absorption of CZX given rectally was rapid in all animals, similar to intramuscular or subcutaneous administration. The peak serum levels of CZX in mice, rats and dogs when administered rectally at a dose of 25 mg/kg were 23.1 micrograms/ml at 7.5 minutes, 23.5 micrograms/ml at 15 minutes and 25.2 micrograms/ml at 15 minutes, respectively. These values were about 76%, 68% and 42% of the values for subcutaneous or intramuscular administration in mice, rats and dogs at the same respective doses. Urinary recoveries of CZX after rectal administration of 25 mg/kg were 44.2% (0-12 12 hours) in rats and 27.7% (0-6 hours) in dogs, and 2.7% (0-6 hours) of the dose was excreted into bile fluid in rats. Organ distribution of CZX when administered rectally to rats was similar in distribution pattern to that of muscular administration, although its concentrations in various organs were slightly lower than those for intramuscular administration, as was the case for serum concentration. Serum concentrations of CZX were proportionately elevated with dose when dogs were rectally administered CZX-S in doses of 12.5, 25 and 50 mg/kg. In the case of multiple administrations (t.i.d. for 10 days) of CZX-S to dogs, no remarkable difference was found in serum concentrations of CZX in comparison with single doses, and no accumulation of CZX was demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)