This medication is used with a doctor-approved exercise, behavior change, and reduced-calorie diet program to help you lose weight. It is used by certain overweight people, such as those who are obese or have weight-related medical problems. Losing weight and keeping it off can lessen the many health risks that come with obesity, including heart disease, diabetes, high blood pressure, and a shorter life. Naltrexone belongs to a class of drugs known as opiate antagonists, and bupropion is an antidepressant that may help restore the balance of certain natural chemicals (neurotransmitters) in your brain. These two medications work together on separate parts of the brain to reduce appetite and how much you eat. Most opiates should not be used for 7 to 10 days before starting naltrexone, but some opiate drugs (such as methadone) should not be used for 10 to 14 days before starting naltrexone. Ask your doctor or pharmacist for more details. Other forms of naltrexone or bupropion are used to treat a variety of conditions including depression, other mental/mood disorders, smoking cessation, addiction to opioid medication, and alcohol abuse. This combination product is not approved for these other uses. Discuss the risks and benefits of this medication, as well as other ways to lose weight, with your doctor.