Short answer: Plain naltrexone tablets (50 mg) are approved for alcohol dependence and for blocking the effects of opioids, not for weight loss. Contrave combines a smaller amount of naltrexone with the antidepressant bupropion, 8 mg/90 mg per tablet, and is approved for long-term weight management in adults.12 Only Contrave has a boxed warning, for suicidal thoughts.
| Naltrexone tablets | Contrave (naltrexone and bupropion ER) | |
|---|---|---|
| What is in it | Naltrexone 50 mg, an opioid blocker1 | Naltrexone 8 mg plus bupropion 90 mg, extended release2 |
| Approved for | Alcohol dependence; blocking the effects of opioids taken from outside the body1 | Weight management with diet and activity in adults with obesity, or overweight with a weight-related condition2 |
| Label dosing | Alcohol: 50 mg once a day. Opioid dependence: 25 mg first, then 50 mg a day if no withdrawal1 | 1 tablet a day, raised weekly to 2 tablets twice a day from week 4 (32 mg naltrexone and 360 mg bupropion a day)2 |
| When to stop (label) | No weight-based rule1 | If under 5% weight loss after 12 weeks on the full dose2 |
| Boxed warning | None1 | Suicidal thoughts and behaviors (bupropion is an antidepressant)2 |
| Opioids | Must be opioid-free first, at least 7 to 10 days after short-acting opioids1 | Not used with chronic opioids; stop it if opioid treatment is needed2 |
| Seizures | Not a listed warning1 | Seizures in about 0.1% vs 0% on placebo; not used with a seizure disorder or an eating disorder2 |
| Half-life of naltrexone | About 4 hours (13 hours for its active metabolite)1 | About 5 hours; bupropion about 21 hours2 |
| Nausea in label studies | 10% in an open-label safety study of about 570 people with alcohol dependence1 | 32.5% vs 6.7% on placebo2 |
No. The naltrexone tablet label lists only alcohol dependence and opioid blockade, and says it has not been shown to help except as part of a plan for addiction.1 Contrave is the product approved for weight management, and it pairs naltrexone with bupropion.2 Taking plain naltrexone for weight is off label, and the labels give no weight results for naltrexone alone.
A plain naltrexone tablet is 50 mg, usually once a day.1 Each Contrave tablet has 8 mg, so the full Contrave dose of 2 tablets twice a day adds up to 32 mg of naltrexone a day, along with 360 mg of bupropion.2 Contrave tablets are not to be cut, chewed or crushed, and the label says not to take them with a high-fat meal because of seizure risk.2
More detail: naltrexone side effects, Contrave side effects, the naltrexone and Contrave dosing schedules, what to do if you miss a Contrave dose, and how to store Contrave.