Pharmacokinetics and metabolism of HOE 077. Preclinical studies

The studies were performed in healthy male rats and in one male dog after oral and intravenous administration of [2-carbamoyl-14C]HOE 077. HOE 077 wa rapidly and completely absorbed after oral administration. In blood, tmax was at about 0.5 h and cmax 2.63 +/- 0.92 micrograms equivalents/g in rats (5 mg/kg), and 18.1 micrograms equivalents/g in the dog (15 mg/kg). The predominant half-lives for total radioactivity were in the range of 1 h in the rats and 2 h in the dog, independent of the route of administration. The radioactivity was distributed throughout the body. The highest concentrations were detected in kidneys and liver. Urine (75% of dose) was the main route of excretion after oral and intravenous administration. The radioactivity was almost entirely eliminated 2 days after administration. The compound was intensively metabolized by rat and dog. While the parent compound was the major component in plasma at early time after dosage, more than ten metabolites, accompanied by only small amounts of original substance, were detected in the urine of the first study day. In faeces only metabolites were found. The known metabolites are assumed to be formed by oxidative degradation of the alkylic side chains of the molecule, preferably that in the 2-position of the pyridine ring. The main metabolite in the dog urine was a 2-hydroxyethyl derivative (M4), and in the rat a hippuric acid analogue of HOE 077 (M6). The pyridine carboxylic acid in 2-position of the side chain of HOE 077 (M2) was the predominant metabolite in faeces of rat and dog. In both animal species, more than 80% of the administered radioactivity had been identified. In rats with liver damage caused by treatment with CCl4 the amount of parent compound increased and the rates of formation of metabolites were lower than in normal rats. This can be interpreted as a consequence of the diminished number of hepatocytes able to metabolize HOE 077.