The absorption and excretion of 1-(2-ethoxyethyl)-2-(4-methyl-1-homopiperazinyl)benzimidazole difumarate (KB-2413) were studied in rats and guinea pigs after oral administration of KB-2413-¹⁴C. Maximum plasma levels (C_max) appeared at 0.25 and 0.5 h after dosing in rats and guinea pigs, respectively. In rats, both C_max and the area under the plasma concentration-time curve (AUC) increased proportionally to the administered dose up to 8mg/kg.
The radioactivity excreted into the urine and the AUC after oral dosing in rats and guinea pigs were close to those after intravenous dosing, and the orally administered radioactivity was almost completely excreted into the bile and urine in the bile-duct-cannulated rats. Thus, it was suggested that KB-2413 was nearly completely absorbed from the intestinal tract of rats and guinea pigs.
The percentages of the radioactivity excreted in feces were 65.3 and 58.9 % of the dose within 96 h after oral administration of KB-2413-¹⁴C in rats and guinea pigs, respectively.
The radioactivity excreted into the bile was about 90 % of the dose within 24 h after oral dosing in bile-duct-cannulated rats. The enterohepatic circulation in rats was suggested, since a considerable amount of the radioactivity was absorbed in the rat which was administered intraduodenally with the bile collected from other rats administered with KB-2413-¹⁴C orally.