[Pharmacokinetics of an ampicillin suppository (KS-R1) in mice, rats and rabbits]

KS-R1, a new suppository of ampicillin (ABPC) sodium, was rectally administered to study its absorption, excretion and distribution in mice, rats and rabbits. Concentrations of ABPC in plasma when 12.5 and 25.0 mg/kg of KS-R1 were rectally administered to experimental animals reached the peak levels rapidly. The values were 7.3 and 13.9 micrograms/ml in mice, 7.7 and 15.9 micrograms/ml in rats, and 14.1 and 35.3 micrograms/ml in rabbits, respectively. All of these values were about 3.5 times as high as those attained by oral administration of the same doses. Concentrations of ABPC in tissues when 25.0 mg/kg of KS-R1 was rectally administered to rats reached the peak level rapidly, as in the concentration in plasma. The concentrations distributed into various tissues were found as follows; liver not equal to kidney greater than spleen greater than heart greater than lung. Urinary recoveries of ABPC after rectal administration of 12.5 and 25.0 mg/kg were 23.4 and 28.4% (0 approximately 12 hours) in rats while 79.4 and 75.4% (0 approximately 6 hours) in rabbits, respectively. When 25.0 mg/kg of KS-R1 was administered to rats, 10.7% of the dose was excreted into bile during 6 hours after administration. The relative bioavailabilities of KS-R1, calculated on the basis of AUC and urinary recovery after parenteral administration of ABPC sodium, were 81.0 to 87.5% in mice, 37.6 to 45.9% in rats and 75.6 to 101% in rabbits, which were 1.5 to 2.8 times higher than those of ABPC orally administered.