Absorption and disposition of oxarbazole in man and laboratory animals

Oxarbazole (9-benzoyl-1,2,3,4-tetrahydro-6-methoxycarbazole-3-carboxylic acid) was absorbed by human volunteers, rats, dogs, guinea pigs, and monkeys. In all species of laboratory animals studied, the major urinary metabolite was the product of O-demethylation, 9-benzoyl-1,2,3,4-tetrahydro-6-hydroxycarbazole-3-carboxylic acid; this metabolite was conjugated in all species except the guinea pig. The dog and monkey excreted small quantities of a conjugate of 1,2,3,4-tetrahydro-6-methoxycarbazole-3-carboxylic acid in the urine. Enterohepatic circulation was demonstrated in bile duct-cannulated rats, in which almost 90% of the radioactivity of a dose of 14C-oxarbazole had been excreted into the bile within 24 hr. At the time of peak blood radioactivity, intact oxarbazole was the major constituent circulating in the bloodstream of rats and monkeys that had received 14C-oxarbazole orally. The clearance of either intact oxarbazole in man and guinea pig, or undifferentiated radioactivity in rat, dog, and monkey, did not follow the kinetics of a simple model.