Pharmacokinetics of an Antiallergic Agent, 1-(2-Ethoxyethyl)-2-(hexahydro-4-methyl-1H-1, 4-diazepin-1-yl)-1H-benzimidazole Difumarate (KG-2413) after Oral Administration : Interspecies Differences in Rats, Guinea Pigs and Dogs

The pharmacokinetics of an antiallergic agent, 1-(2-ethoxyethyl)-2-(hexahydro-4-methyl-1H-1, 4-diazepin-1-yl)-1H-benzimidazole difumarate (KG-2413) after oral administration were studied in rats, guinea pigs and dogs. Maximum plasma level (Cmax) appeared at 23, 32 and 51 min after dosing in rats, guinea pigs and dogs, respectively. Plasma half-lives of the terminal phase were comparable to those after intravenous administration in each animal species. Pronounced interspecies differences were observed in the Cmax/dose and area under the plasma concentration-time curve (AUC)/dose, namely, these values were high in guinea pigs and low in rats and dogs. The extents of bioavailability were 0.036 in rats (20 mg/kg), 0.50 in guinea pigs (2 mg/kg) and 0.052 in dogs (2 mg/kg). These variations in the pharmacokinetic parameters in the animals were assumed to be mostly due to the species difference in the hepatic intrinsic clearance.