Biosynthesis, isolation, and identification of 6-beta-hydroxynaltrexone, a major human metabolite of naltrexone

Chemical reduction of naltrexone is described in an attempt to synthesize 6-beta-hydroxynaltrexone. Only the epimer, 6-alpha-hydroxynaltrexone, was produced. Pilot metabolic studies on naltrexone in the dog, rat, and guinea pig were made to determine which animal produced the greatest amount of 6-beta-hydroxynaltrexone. The guinea pig was selected and used to produce the metabolite. Isolation and purification methods are described, and spectral data are presented for structural confirmation of the metabolite.