Key Points

• Weight gain is not a common side effect with oral naltrexone treatment. Naltrexone is approved to help promote weight loss when used in combination with bupropion (brand name: Contrave).
• Naltrexone is known to frequently cause stomach side effects like nausea and vomiting (10% or more of patients), stomach pain or cramping, and loss of appetite which could contribute to weight loss. These side effects may lessen over time.
• Oral naltrexone has been reported by the manufacturer to cause both weight gain and increased appetite, but these are not frequent adverse events.

Naltrexone when combined with bupropion (brand name: Contrave) is used to help with weight loss. Contrave is an extended-release form of two FDA-approved drugs, oral naltrexone tablets and oral bupropion (Wellbutrin SR).

Contrave is used in obese or overweight adults with at least one weight-related condition such as high blood pressure or type 2 diabetes. It is used in addition to diet and exercise. In clinical trials, 36% to 48% of patients taking Contrave lost at least 5% of body weight.

Naltrexone is an opioid antagonist approved to treat alcohol or opioid dependence (following detoxification) along with group counseling. Bupropion is classified as an antidepressant and is used to treat depression, seasonal affective disorder and as an aid to quit smoking.

Learn more: FDA Approved Weight Loss Drugs - Can They Help You?