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Naltrexone

Three naltrexone products sit on this shelf: Revia at 50 mg, Mysimba at 90 mg combined with bupropion, and Low Dose Naltrexone Capsules at 1.5 mg. This opioid antagonist is used for alcohol dependence, opioid dependence and, in combination with bupropion, weight management.

Low Dose Naltrexone Capsules

Fibromyalgia

1.5mg

Naltrexone capsules for fibromyalgia and fatigue in multiple sclerosis. This low dose is far below the addiction-treatment amount.

From$2.13/ capsuleView

Mysimba

Chronic Weight Management

90mg + 8mg

Naltrexone and bupropion tablets for weight management. They work on the brain's reward system to cut food cravings.

From$2.89/ tabletView

Revia

Alcohol Dependence, Opioid Dependence

50mg

Naltrexone tablets for alcohol and opioid dependence. They block the reward effects of these substances, reducing craving.

From$3.84/ tabletView

Key points

  • Naltrexone blocks opioid receptors, so starting it while opioids remain in the body can trigger a withdrawal reaction. An opioid-free interval of at least 7 to 10 days is recommended after short-acting opioids, extending to two weeks after buprenorphine or methadone.
  • Mysimba pairs 90 mg naltrexone with 8 mg bupropion in a prolonged-release tablet, indicated for weight management alongside a reduced-calorie diet and increased physical activity.
  • The label warns of hepatitis and liver dysfunction associated with naltrexone exposure; patients should seek medical attention for symptoms of acute hepatitis and stop treatment if they appear.

How does Naltrexone work?

Naltrexone is an opioid antagonist, meaning it binds to opioid receptors in the brain and reversibly blocks the effects of opioids taken from outside the body. A person who takes naltrexone and then uses an opioid will not feel the euphoria or sedation that drug would normally produce.

At 50 mg, Revia occupies enough receptors to block opioid effects for a full day. In Mysimba, the 90 mg naltrexone component works alongside bupropion to support weight management in adults who meet a body-mass-index threshold. At the much lower 1.5 mg dose in Low Dose Naltrexone Capsules, the same receptor-blocking action is listed for Fibromyalgia and Multiple Sclerosis-associated Fatigue.

Brands and forms in this catalogue

Revia is the brand-name 50 mg tablet, listed for alcohol dependence and opioid dependence. Mysimba is a separate brand-name product from Orexigen Therapeutics: a prolonged-release tablet that combines naltrexone with bupropion for chronic weight management. Low Dose Naltrexone Capsules carry just 1.5 mg in a capsule and appear under Pain & Anti-inflammatories for fibromyalgia and MS-associated fatigue.

The two forms matter for how you take the medicine. Revia and Mysimba are tablets; Mysimba’s prolonged-release design means the naltrexone and bupropion are released slowly over hours rather than all at once. The capsule form of Low Dose Naltrexone Capsules delivers a fraction of the dose found in Revia, which is why it sits in a different category and serves a different purpose on the shelf.

Further reading