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What Is Naltrexone?

Naltrexone is a prescription opioid antagonist used to treat alcohol use disorder and to prevent relapse to opioid dependence after opioid detoxification. It blocks opioid receptors without producing opioid intoxication. Naltrexone is available as oral tablets and an extended-release intramuscular injection. It is used alongside counseling and other support as part of a broader treatment plan.

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What Is Naltrexone?

Naltrexone is a prescription opioid antagonist used to treat alcohol use disorder and to prevent relapse to opioid dependence after opioid detoxification. It blocks opioid receptors without producing opioid intoxication. Naltrexone is available as oral tablets and an extended-release intramuscular injection. It is used alongside counseling and other support as part of a broader treatment plan.

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How Does Naltrexone Work?

Naltrexone blocks opioid receptors, preventing opioids from producing their usual effects. In alcohol use disorder, it can reduce the rewarding effects of alcohol and help decrease cravings or heavy drinking. Naltrexone does not cause an alcohol-like aversive reaction when alcohol is consumed. It also does not relieve acute opioid withdrawal symptoms.

Who Can Receive Naltrexone Treatment?

People with alcohol use disorder or opioid use disorder may be candidates for naltrexone. For opioid use disorder, patients must complete opioid withdrawal and remain opioid-free for the recommended period before treatment begins. People taking opioid pain medicines or those with current opioid dependence should not start naltrexone. Clinicians also review liver health, pregnancy considerations, and other medicines before prescribing it.

How Is Naltrexone Taken?

Oral naltrexone is commonly prescribed as a 50 mg tablet taken once daily, although schedules can vary. The extended-release injection is typically administered by a healthcare professional once every four weeks or monthly. Before treatment for opioid use disorder, an opioid-free period of at least seven to ten days is generally recommended, and longer periods may be required after buprenorphine or methadone. Follow the specific formulation's prescribing instructions.

What Are the Risks and Side Effects of Naltrexone?

Common side effects include nausea, headache, dizziness, tiredness, and sleep disturbances. Extended-release injections can cause injection-site reactions, including rare severe tissue injury. Naltrexone can cause liver injury, and starting it too soon after opioid use can precipitate severe withdrawal. After treatment ends, reduced opioid tolerance increases overdose risk if opioids are resumed.

Common Questions About Naltrexone

Does naltrexone help reduce alcohol cravings?

Naltrexone can reduce alcohol cravings and heavy drinking for some patients. Treatment outcomes vary and are supported by counseling and follow-up care.

Can naltrexone be taken with opioid painkillers?

Naltrexone blocks opioid medications and can interfere with pain relief. Tell every treating clinician about naltrexone use, especially before surgery or emergency pain treatment.

How long must someone avoid opioids before starting naltrexone?

An opioid-free interval of at least seven to ten days is commonly required. People previously taking methadone or buprenorphine may need a longer interval under medical supervision.

Is naltrexone the same as naloxone?

No. Both block opioid receptors, but naloxone is used for emergency overdose reversal. Naltrexone is used for ongoing treatment of alcohol use disorder and prevention of opioid relapse after detoxification.

References

DailyMed - NALTREXONE HYDROCHLORIDE tablet, film coated. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=adb7c4dc-221a-4d91-9687-0d78913a92ad. Date Accessed October 16, 2026.

Naltrexone. LiverTox. https://www.ncbi.nlm.nih.gov/books/NBK548583/. Date Accessed October 16, 2026.

Naltrexone. MedlinePlus. https://medlineplus.gov/druginfo/meds/a685041.html. Date Accessed October 16, 2026.

Naltrexone. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Naltrexone. Date Accessed October 16, 2026.

Naltrexone. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK534811/. Date Accessed October 16, 2026.