METABOLISM IN VITRO AND IN VIVO OF PENTAZOCINE

The metabolism of pentazocine has been investigated in the 10,000 g supernatant of monkey, mouse and rat liver homogenates and in the monkey, in vivo. Extracts of the incubations in vitro and of monkey urine were examined for pentazocine and possible metabolites. Tritium-labeled pentazocine was used to quantitate the excretion of the drug after administration and to measure the recovery of metabolites. The results indicate that the metabolism of pentazocine occurs mainly through oxidation of the terminal methyl groups of the dimethylallyl side-chain to yield two isomeric alcohols and one of the corresponding carboxylic acids. Some of the pentazocine and its metabolites were present in the urine as unidentified conjugates. About 70 per cent of the radioactivity administered as pentazocine was recovered in 24 hr in the urine of monkeys receiving widely varying doses of the drug. © 1969.