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Naltrexone can support your recovery from opioid or alcohol use disorder.

Naltrexone is a medication used to treat alcohol use disorder (AUD) and opioid use disorder (OUD). Naltrexone helps reduce cravings for alcohol or opioids by blocking the effects of these substances.

Naltrexone is available as an oral tablet, taken daily, or as an extended-release injection, which causes the medication’s effects to last for four weeks.

Recovery from alcohol and opioid use disorders is possible, and naltrexone may help.

What is naltrexone?

Naltrexone is a medication that can block the intoxicating effects of alcohol or opioids on the body. Naltrexone first received Food and Drug Administration (FDA) approval in 1994 as a 50-milligram oral tablet for treating AUD. The extended-release injectable form was approved to treat AUD in 2006 and OUD in 2010.

Naltrexone can be an effective part of medication treatment for AUD or OUD. Formerly known as medication-assisted treatment (MAT) programs, medication for AUD or OUD programs combine medication such as naltrexone with counseling or behavioral therapies. These programs can help you or a loved one adjust to life in recovery, remain in treatment, follow prescribed therapies, and address other physical and mental health issues.

Low-dose naltrexone is sometimes prescribed to treat chronic pain. It is also combined with bupropion for use as a weight loss medication. However, bupropion is generally not advised for patients with AUD because of the risk of seizures and other harmful side effects.

Naltrexone for alcohol use disorder


Naltrexone can be prescribed as a once-daily tablet (marketed as Revia) or as a monthly extended-release injection (marketed as Vivitrol) to treat AUD. It blocks the pleasant effects of using alcohol and therefore combats cravings. Other FDA-approved drugs to treat alcohol dependence are disulfiram and acamprosate.

Ideal candidates for this therapy are people with moderate to severe dependence on alcohol who can abstain from alcohol for a few days before starting treatment.


Naltrexone is effective in helping people cut back on or stop alcohol use. Research shows that people taking a daily 50-milligram dose increased the percentage of alcohol-free days and reduced the frequency of heavy drinking days. And an evaluation of the 380-milligram dose of extended-release naltrexone found it helped patients reduce by 25% the frequency of heavy drinking days; in that study, it was more effective among men than among women.

What is the most effective medication for AUD?

There are three major medications for AUD: acamprosate, disulfiram, and naltrexone. The best AUD treatment medication for you depends on your health goals, medical conditions, and medical history.

Acamprosate is generally seen as most effective for people who are already abstaining from drinking and people who are using opioids or other medications that interact poorly with naltrexone. 

Disulfiram is most effective when its use by otherwise healthy, alcohol-free patients is closely monitored and paired with counseling and education. It is considered a second-line treatment, after acamprosate and naltrexone. 

Naltrexone generally works best for people with moderate to severe dependence on alcohol who want to cut back on or eliminate alcohol use.

Naltrexone for opioid use disorder


While the oral formulation of naltrexone is used only to treat alcohol use disorder, extended-release naltrexone is FDA-approved to treat both alcohol and opioid use disorders. For people with an OUD, extended-release naltrexone is administered as a 380-milligram injection into muscle. Patients receive a shot from trained medical providers every four weeks. The drug treats OUD by binding to and blocking the brain’s opioid receptors. This stops opioids from producing a “high” — that is, their relaxing and euphoric effects — and can prevent cravings for the drug.

Patients must stop using opioids before receiving extended-release naltrexone. During this opioid withdrawal period, patients are sometimes given medications to make the process more comfortable.

Although naltrexone is considered safe, your health care provider must perform thorough screening, diligent testing, and careful monitoring to ensure that it works as intended. Extended-release naltrexone is not recommended for people who:

  • Are experiencing active withdrawal from opioids.
  • Are currently using opioids.
  • Have taken short-acting opioids in the past 10 days, or long-acting opioids, including methadone and buprenorphine, in the past 14 days.

Research shows that buprenorphine and methadone are most effective in treating opioid use disorders. However, extended-release naltrexone has some benefits. Naltrexone is not habit-forming. And because medical providers administer the shot, extended-release naltrexone will always be taken as prescribed.

What is the difference between naltrexone and naloxone?

Both medications block the effects of opioid use. But while naltrexone is intended for long-term treatment of OUD or AUD, naloxone — marketed as Narcan, Zimhi, or Kloxxado — is used in an emergency to stop the toxic effects of an opioid overdose. Naloxone is available as a prefilled syringe or nasal spray.

Learn more about naloxone.

Side effects and precautions

Side effects

Before taking this or any medication, consult with a medical professional. Common side effects of oral and extended-release naltrexone include:

  • Nausea or vomiting.
  • Dizziness.
  • Fatigue.
  • Headache, upper abdominal pain, or back pain.
  • Decreased appetite.
  • Liver damage or hepatitis.
  • Allergic reactions.
  • Depression.

Taking extended-release naltrexone can also cause a localized reaction at the injection site.


Data shows that naltrexone is less likely to prevent opioid overdose than buprenorphine or methadone. This may be because it is difficult for people with OUD to stop using opioids for long enough to safely begin naltrexone. It also may be because naltrexone, unlike buprenorphine and methadone, is not itself an opioid.

Individuals must be screened for opioid use before beginning naltrexone treatment. For anyone with opioids still in their system before treatment, or anyone who takes opioids during treatment, this medication may cause withdrawal symptoms because it interferes with the effects of opioids on the brain. Withdrawal symptoms may include feelings of distress and irritability, irregular heartbeat, shaking, sweating, and even depression and thoughts of suicide.

If you are switching from buprenorphine or methadone to naltrexone, work with your medical provider to mitigate the risk of withdrawal and manage any withdrawal symptoms from stopping those medications.

Extended-release naltrexone is not safe or appropriate for everyone. Review the following precautions to determine whether extended-release naltrexone is right for you:

  • If you are hypersensitive to the medication, you could experience a rash, swelling, or anaphylaxis.
  • If you have a liver disease (like cirrhosis), a kidney disease, or a bleeding or coagulation disorder, treatment with naltrexone may worsen symptoms.
  • If you are being treated with naltrexone, you must avoid opioid-based pain medication. If you plan to take opioid-based pain medications — for example, if you are going to have surgery — you must stop extended-release naltrexone 28 days beforehand and oral naltrexone 72 hours beforehand.

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Considerations before taking

Safety and toxicity. Naltrexone does not cause dependence or intoxication, but taking higher doses than prescribed can be toxic to the liver.

Risk of opioid overdose. People who resume using opioids during or after naltrexone treatment may have an elevated risk of overdose, especially if they use large amounts of opioids to overcome the naltrexone’s blocking effects. Naltrexone can also decrease tolerance for opioids and make people more sensitive to their effects. This sensitivity can heighten the risk of overdose in someone who stops taking naltrexone and then takes a “regular” dose of opioids.

Once injected, extended-release naltrexone remains in the body for approximately 28 days. It will block the effects of opioids for about that length of time.

Pregnancy and breastfeeding. Initiating naltrexone for OUD requires going through the opioid withdrawal process, which may be dangerous in pregnancy for both the pregnant person and the fetus. However, a pregnant person who is already taking naltrexone, or who would like to start naltrexone for AUD and who is not using opioids, may be able to safely take naltrexone during pregnancy. If you are planning a pregnancy, are pregnant, or are breastfeeding, talk with your medical provider about whether you can safely take naltrexone. Little naltrexone is excreted into breast milk, so breastfeeding while taking naltrexone is generally considered safe.

Interactions. Before taking naltrexone, make sure your system is free of opioids. In addition to being free of opioids, you should not drink alcohol, take sedatives, or use certain other types of drugs while taking naltrexone. Talk to your medical provider or pharmacist about possible interactions with any other drugs you’re taking, including over-the-counter medicines, vitamins, and supplements.

Cost. A 30-day supply of the oral form of naltrexone costs around $48, but you could pay less with insurance and retailer discounts. Extended-release naltrexone generally costs more out of pocket than methadone or buprenorphine does. Actual costs vary, but one study estimated that this treatment costs on average about $48 per day without insurance compared with about $13 per day for methadone and $21 per day for buprenorphine. However, patients with insurance may pay less. In addition, Medicaid and Medicare may cover this treatment. Visit the Centers for Medicare & Medicaid Opioid Prescribing page for more information.

If you are uninsured, are underinsured, or otherwise have trouble paying for treatment, ask a naltrexone treatment center near you whether it can help you obtain free or subsidized care.

Other considerations. This treatment is most effective when combined with supportive counseling or medical care. Because extended-release naltrexone has long-lasting physical effects, carry a card that says you are using this medication; first responders will look for this card in an emergency.

Find naltrexone treatment near you

Content reviewed by Jasleen Salwan, M.D., MPH, FASAM, April 2023. 


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