Naltrexone

Key points

• Naltrexone is an opioid antagonist used to treat alcohol dependence and to block the effects of opioids taken from outside the body.
• Naltrexone has a measured elimination half-life of about 4 hours, and its active metabolite 6-beta-naltrexol has a longer measured half-life of about 13 hours.
• Before starting treatment, a naloxone challenge test or a urine screen for opioids can help confirm that a patient is free of opioids.
• Mysimba combines naltrexone with bupropion and is indicated, alongside a reduced-calorie diet and increased activity, for weight management in adults who meet a body-mass-index threshold.

Naltrexone alone: opioid-free timing and liver safety

Revia and Naltrexone Tablets each contain naltrexone alone at 50 mg and connect to alcohol dependence within the addiction recovery category. Naltrexone blocks opioid receptors, so starting it while opioids remain in the body can bring on a withdrawal reaction. The naltrexone hydrochloride tablet label recommends an opioid-free interval of at least 7 to 10 days for patients coming off short-acting opioids, extending to as long as two weeks for patients switching from buprenorphine or methadone.

The same label records cases of hepatitis and clinically significant liver dysfunction associated with naltrexone during its clinical development and after launch. It advises seeking medical attention for symptoms of acute hepatitis and stopping naltrexone if they appear.

Mysimba: naltrexone combined with bupropion

Mysimba, which connects to chronic weight management, combines naltrexone with bupropion and is indicated, alongside a reduced-calorie diet and increased physical activity, for weight management in adults who meet a body-mass-index threshold. Because Mysimba contains bupropion, its summary of product characteristics links the combination to the antidepressant-class signal for a higher rate of suicidal thinking and behaviour among younger patients in placebo-controlled trials, and it records that suicidality events, including suicidal ideation, have been reported in patients of all ages since launch.

The same document calls for close supervision of patients on Mysimba, especially early in treatment and after dose changes, and advises patients and caregivers to watch for clinical worsening, suicidal thoughts or behaviour, or unusual changes in behaviour, and to seek medical advice immediately if these appear.

Contrave: a regional name for the combination

Naltrexone with bupropion is also recorded in the region under the Contrave name. The Emirates Drug Establishment’s drug directory lists Contrave 8 mg/90 mg with bupropion hydrochloride and naltrexone hydrochloride as its combination, a familiar regional name for readers who know the medicine this way.

Further reading

• NALTREXONE HYDROCHLORIDE tablet, film coated
• Mysimba 8 mg/90 mg prolonged-release tablets
• Contrave® 8 mg/90 mg - Drug Directory