Isolation and identification of urinary metabolites of oxycodone in rabbits

Metabolism of oxycodone was studied in the rabbit and found to proceed through five metabolic pathways: O-demethylation, N-demethylation, N-oxidation, 6-keto reduction, and glucuronidation. Six urinary metabolites were isolated and identified in the unconjugated form: 14-hydroxydihydromorphinone, 14-hydroxydihydrocodeine, 14-hydroxydihydrocodeinone N-oxide (oxycodone N-oxide), 14-hydroxydihydroisocodeine, 14-hydroxydihydrocodeine N-oxide, and noroxycodone, together with unchanged oxycodone. Identification was made by means of various chromatographic and spectral comparisons with authentic samples. Oxycodone, 14-hydroxydihydromorphinone, 14-hydroxydihydrocodeine, 14-hydroxydihydroisocodeine, and noroxycodone were also identified as aglycons of conjugated metabolites.