Once-A-Month Naltrexone Injection

Improves Long-Term Treatment Outcomes

A woman talking to a healthcare provider.

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Naltrexone injection is a medication that is used in conjunction with other methods to help people who have quit consuming alcohol maintain their sobriety. The medication has become one of the most effective pharmaceutical treatments for alcohol use disorder because it works to reduce the chemical effects that alcohol has on the brain.


Naltrexone can be prescribed for a few different uses. These include:

  • Alcohol dependence: One of only three medications approved for the treatment of alcohol dependence, naltrexone has been used for years to help people who have already stopped drinking to avoid relapse.
  • Opioid dependence: Naltrexone has also been effective in treating people who have become addicted to prescription opioids and heroin. It is being researched for use in treating cocaine use disorders. It works for treating these conditions by blocking the effect that opioids have on the pleasure centers of the brain.
  • Other uses: In lower doses, naltrexone is also used to treat pain caused by conditions like fibromyalgia and chronic fatigue syndrome.

Daily Pill vs. Monthly Injection

Naltrexone is available as both a daily pill and a monthly injection. While both medications are effective, there are some clear benefits to a long-lasting, once-a-month injection.

Daily Naltrexone Pill

For the treatment of alcohol use disorders, naltrexone was originally prescribed as a daily pill usually taken for a period of about 12 weeks. Naltrexone in pill form—marketed as ReVia and Depade—is still widely used.

However, there is an inherent problem with the pill form of naltrexone: It has to be taken every single day in order for it to work. For those struggling with the effects of alcohol withdrawal and alcohol use disorder, compliance with taking a daily dose can be problematic. It's easy to forget to take a dose, to accidentally take two doses, or to intentionally skip it because of feelings of nausea associated with alcohol withdrawal.

Monthly Naltrexone Injection

This problem was addressed when researchers began to look at a new form of naltrexone that could be injected once and be slowly released into the system for a month. The research found that once-a-month naltrexone was effective in reducing alcohol use.

Before Taking

Before initiating treatment with injectable naltrexone, your healthcare provider will perform a physical exam, determine your liver function, and conduct a drug test. Because naltrexone is an opioid antagonist, taking it may lead to opioid withdrawal.

It is important to be opioid-free for a certain period of time before you begin receiving naltrexone injections.

Precautions and Contraindications

You should not receive monthly naltrexone injections or take other naltrexone-containing medications if you are using opioids. The Substance Abuse and Mental Health Services Administration (SAMHSA) suggests that people who are being treated with naltrexone may have a reduced tolerance to opioids. This can lead to potentially life-threatening consequences when people take opioids at the same levels they previously used. Accidental overdose can occur, which may result in death.

Because the injection medication bypasses the first-pass metabolism by the liver, the injectable form may reduce the risk of liver toxicity. However, the Food and Drug Administration (FDA) warns of the potential for liver toxicity if naltrexone is taken at levels higher than the recommended dose. Monthly naltrexone injections should not be used by people who have acute hepatitis or liver failure. 

How to Take

If you believe that you have an alcohol use disorder or want to cut back on your drinking, talk to your doctor about your treatment options. Your doctor will perform an evaluation of your health and needs to determine if a monthly naltrexone injection is right for you.

If your doctor determines that this approach might be appropriate, your doctor will give you an intramuscular injection in the gluteal muscles every four weeks. You may find that medication adherence is easier than taking a daily pill because it only requires one injection each month.

Side Effects

The side effects of monthly naltrexone injections are similar to those of daily oral naltrexone. Possible side effects may include:

  • Abdominal pain
  • Back pain
  • Decreased appetite
  • Dizziness
  • Fatigue
  • Headache
  • Injection site reactions
  • Joint pain
  • Muscle aches
  • Vomiting

In one large study, of those taking a 380 milligram dose, 14.1% dropped out of the treatment due to side effects, including nausea, headache, and fatigue. Only 6.7% of the group receiving 190 milligrams discontinued treatment due to adverse side effects.

The study was one of the largest trials of subjects treated with medication for alcohol dependence. The researchers concluded that extended-release naltrexone was well tolerated and significantly reduced heavy drinking in actively drinking individuals.

Severe side effects can also occur in some cases. These may include:

  • Allergic reactions
  • Feelings of depression
  • Liver damage
  • Reactions at the injection site (which may be severe and require intervention)
  • Suicidal thoughts or behaviors

If you are having suicidal thoughts, contact the National Suicide Prevention Lifeline at 1-800-273-8255 for support and assistance from a trained counselor. If you or a loved one are in immediate danger, call 911.

You should seek medical attention immediately if you begin to experience signs of a serious allergic reaction, including trouble breathing, difficulty swallowing, or swelling of your mouth, face, or hands.


One study indicated that the injection of a 380 mg dose of naltrexone resulted in a 25% reduction of heavy drinking days, while a 190 mg dose reduced heavy drinking days 17%.

Research suggests that men may to naltrexone treatment more than women and that those who begin treatment after a period of drug or alcohol abstinence may experience greater treatment effects. The long-acting form of naltrexone may improve treatment strategies for people with alcohol dependence by eliminating the medication compliance issue.

The Food and Drug Administration approved the once-a-month naltrexone treatment—marketed as Vivitrol—for use as a treatment for alcohol dependence in 2006. In 2010, the FDA also approved the use of Vivitrol to treat people with opioid dependence. 

If you or a loved one are struggling with substance use or addiction, contact the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 1-800-662-4357 for information on support and treatment facilities in your area.

For more mental health resources, see our National Helpline Database.

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