Journal of analytical toxicology
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Naltrexone is effective in treating opioid dependence by blocking µ, κ and δ opiate receptors. Naltrexone is mainly metabolized to an active metabolite 6β-naltrexol by dihydrodiol dehydrogenase enzymes. Concomitant opioids will not be effective while patients are taking this antagonist. ⋯ Eighteen of 88 patients taking oral naltrexone tested positive for concomitant opiate use. Urinary MRs of 6β-naltrexol/naltrexone were highly variable, which may contribute to variability in efficacy, toxicity and patient willingness to take naltrexone as directed. Twenty percent of patients tested positive for opiates and naltrexone, thus showing the importance of monitoring patients taking naltrexone.