[Metabolic fate of 14C-isepamicin sulfate (14C-HAPA-B) in rats. I. Absorption, distribution, metabolism and excretion after a single intramuscular and intravenous administration].

Absorption, distribution, metabolism and excretion of 14C-isepamicin sulfate (14C-HAPA-B) following a single intramuscular and intravenous administration of 25 mg/kg were studied in male rats. After an intramuscular administration, the drug was rapidly absorbed and the maximum plasma level of about 75 micrograms/ml was obtained at 10 minutes after the administration. The plasma levels rapidly decreased following either intramuscular or intravenous route. The HAPA-B was rapidly distributed into tissues except the central nervous system and the eye ball. Especially high concentrations were attained in kidney and cartilage tissues, concentrations in lung followed these tissues. Radioactivity remained in kidney for a long period, but it disappeared from cartilage and other tissues rapidly. The radioactivity in kidney was located in the cortex at 24 hours after administration. There was no difference in the distribution of radioactivity with different administration routes. The HAPA-B was mainly excreted in the urine following either intramuscular or intravenous administration. Approximately 80% of the dose by intramuscular and 92% by intravenous administrations were excreted during the first 4 hours. Within 24 hours, over 95% was recovered in either routes. The radioautogram of the thin-layer chromatography of the 0 approximately 16-hour urine showed a single radioactive zone with an identical Rf value to HAPA-B. Binding ratios of 14C-HAPA-B to plasma protein were less than 10% both in vitro and in vivo and to erythrocytes less than 9% in vitro.