Abstract

Pooled urine samples from patients receiving 100-200 mg of naltrexone per day orally were extracted; the basic (alkaloid) compounds derived were isolated by preparative thin-layer chromatography. The major metabolite of naltrexone was found to be an epimer of N-cyclopropylmethyl-14-hydroxy-7,8-dihydronormorphine wherein the 6-keto group of naltrexone had been reduced to yield the 6β-hydroxy epimer (an isomorphine). This conclusion was based on infrared, mass, and nuclear magnetic resonance spectra studies. Furthermore, the reduction product formed in vitro in a soluble chicken liver enzyme system from naltrexone and an in vivo metabolite of naloxone derived from the chicken were found to have the more commonly expected 6α-hydroxy orientation.