[Absorption and excretion of an ampicillin suppository (KS-R1) in dogs]

KS-R1, a new suppository of ampicillin (ABPC) sodium, was compared with the widely used oral ABPC and parenteral ABPC sodium in terms of absorption and excretion in mature and infant Beagle dogs. Plasma levels of ABPC in mature dogs when administered rectally with 12.5 and 25.0 mg/kg of KS-R1 reached the respective peaks of 8.0 and 13.5 micrograms/ml in 10 to 20 minutes. Thereafter, the plasma levels declined with biological half-lives of 0.72 and 0.93 hours, respectively. During the first 6 hours after administration of 12.5 mg/kg, 14.3% of the dose was excreted in urine. The relative bioavailability of KS-R1, calculated on the basis of AUC and urinary recovery after intramuscular administration of ABPC sodium, was 23.1% to 28.9%, compared with 31.1% to 50.2% in the case of oral ABPC. Plasma levels of ABPC in infant dogs rectally administered with 12.5 mg/kg of KS-R1 reached 11.9 microgram/ml in 10 minutes, and then declined with biological half-life of 1.24 hours. During the first 6 hours after rectal administration, 31.9% of the dose was recovered in the urine. The relative bioavailability of KS-R1 in infant dogs was 53.8% to 58.0%, which was better than that of mature dogs and was equal to that of oral ABPC. In the case of multiple doses of KS-R1 to mature dogs, no remarkable difference was found in concentration in plasma, and no accumulation of ABPC was demonstrated. Macroscopically, no remarkable abnormality was found at all around the sites of continuous administration.