The hydrochloride salt of naltrexone, a noroxymorphone derivative with competitive opioid antagonistic activity.
Naltrexone and its metabolite 6-beta-naltrexol reverse the effects of opioids by binding to various opioid receptors in the central nervous system (CNS), including the mu-, kappa-, and gamma-opioid receptors; opioid effects of analgesia, euphoria, sedation, respiratory depression, miosis, bradycardia, and physical dependence are inhibited.
Naltrexone is longer-acting and more potent than naloxone.
Opioid dependence. Initial: 25 mg, then up to 50 mg/day if no withdrawal signs. Maintenance: 350 mg/wk given as 50 mg/day or divided in 3 doses (given on 3 days of the wk) for improved compliance.
Adjunct in alcohol dependence: 50 mg/day.
Adjunct in alcohol dependence: 380 mg 4 wkly.
Adverse drug reactions: abdominal pain, nausea, vomiting, anxiety, insomnia, lethargy, headache, musculoskeletal pain, anorexia, diarrhea, constipation, liver function abnormalities.