Naltrexone is a medication used in medication-assisted treatment (MAT) to treat both opioid and alcohol use disorders. What Is Naltrexone? Naltrexone is a medication approved by the Food and Drug Administration (FDA) to treat opioid use disorders and alcohol use disorders. It comes in a pill form or as an injectable. The pill form of naltrexone (ReVia, Depade) can be taken at 50 mg once per day. The injectable extended-release form of the drug (Vivitrol) is administered at 380 mg intramuscular once a month. Naltrexone can be prescribed by any health care provider who is licensed to prescribe medications. To reduce the risk of precipitated withdrawal, patients are warned to abstain from illegal opioids and opioid medication for a minimum of 7-10 days before starting naltrexone. If switching from methadone to naltrexone, the patient has to be completely withdrawn from the opioids. How Naltrexone Works Naltrexone blocks the euphoric and sedative effects of drugs such as heroin, morphine, and codeine. It works differently in the body than buprenorphine and methadone, which activate opioid receptors in the body that suppress cravings. Naltrexone binds and blocks opioid receptors, and is reported to reduce opioid cravings. There is no abuse and diversion potential with naltrexone. If a person relapses and uses the problem drug, naltrexone prevents the feeling of getting high. People using naltrexone should not use any other opioids or illicit drugs; drink alcohol; or take sedatives, tranquilizers, or other drugs. If patients on naltrexone discontinue use, they may have reduced tolerance to opioids and may be unaware of their potential sensitivity to the same, or lower, doses of opioids that they used to take. If patients who are treated with naltrexone relapse after a period of abstinence, it is possible that the dosage of opioid that was previously used may have life-threatening consequences, including respiratory arrest and circulatory collapse. As with all medications used in medication-assisted treatment (MAT), naltrexone is to be prescribed as part of a comprehensive treatment plan that includes counseling and participation in social support programs. Naltrexone for Opioid Use Disorders Extended-release injectable naltrexone is approved for treatment of people with opioid use disorder. It can be prescribed by any healthcare provider who is licensed to prescribe medications, special training is not required. It is important that medical managed withdrawal (detoxification) from opioids be completed at least 7 to 10 days before extended-release injectable naltrexone is initiated or resumed. Research has shown that naltrexone decreases reactivity to drug-conditioned cues and decreases craving. If patients who have been treated with extended-release injectable naltrexone discontinue use, they may have reduced tolerance to opioids and may be unaware of their potential sensitivity to the same, or lower, doses of opioids that they used to take. Extended-release naltrexone should be part of a comprehensive management program that includes psychosocial support. Naltrexone for Alcohol Dependence When used as a treatment for alcohol dependency, naltrexone blocks the euphoric effects and feelings of intoxication. This allows people with alcohol addiction to stop or reduce their drinking behaviors enough to remain motivated to stay in treatment and avoid relapses. Naltrexone is not addictive. Long-term naltrexone therapy extending beyond three months is considered most effective by researchers, and therapy may also be used indefinitely. Learn more about alcohol use disorders. Side Effects of Naltrexone If people taking naltrexone experience side effects, they should consult their health care provider or substance misuse treatment practitioner to adjust the dose or change the medication. Some side effects include: Upset stomach or vomiting Diarrhea Headache Nervousness Sleep problems/tiredness Joint or muscle pain Seek a health care provider right away for: Liver injury: Naltrexone may cause liver injury. Seek evaluation if have symptoms and or signs of liver disease. Injection site reactions: This may occur from the injectable naltrexone. Seek evaluation for worsening skin reactions. Allergic pneumonia: It may cause an allergic pneumonia. Seek evaluation for signs and symptoms of pneumonia. Resources and Publications Clinical Advances in Non-agonist Therapies: Meeting Proceedings – 2016 (PDF | 654 KB) Advisory: An Introduction to Extended-Release Injectable Naltrexone for the Treatment of People with Opioid Dependence – 2012 Clinical Use of Extended-Release Injectable Naltrexone in the Treatment of Opioid Use Disorder: A Brief Guide – 2014 Evidence for the Efficacy of Naltrexone in the Treatment of Alcohol Dependence – 2002 (PDF | 180 KB) TIP 63: Medications for Opioid Use Disorder – Introduction to Medications for Opioid Use Disorder Treatment (Part 1 of 5) – 2019 Training on Providing Naltrexone MAT services professionals must acquire and maintain certification to legally dispense and prescribe medications for opioid and alcohol dependency. SAMHSA’s Division of Pharmacologic Therapies (DPT) provides opioid prescribing courses for physicians; webinars, workshops, and summits; and publications and research.