Naltrexone is a prescription medication that is primarily used to help treat opioid dependence and alcohol use disorder. It works by blocking opioid receptors in the brain, which prevents the euphoric and sedative effects of opioids and helps reduce cravings for alcohol and opioids. Unlike opioid medications, naltrexone does not produce a “high” and is not considered addictive. It is available in both oral tablet form and as a long-acting injectable formulation that is given once a month. Doctors usually prescribe naltrexone as part of a comprehensive treatment plan that may include counseling, behavioral therapy, and support programs. Because it can trigger withdrawal symptoms in people who are currently using opioids, patients must be opioid-free for a period of time before starting the medication. Common side effects may include nausea, headache, dizziness, fatigue, and stomach discomfort, and it should be used under medical supervision, especially in people with liver conditions.