Uses and Side Effects

Naltrexone is a medication doctors prescribe to help reduce alcohol and opioid dependence. 1 It’s possible to struggle with one or both addictions and benefit from taking naltrexone. Doctors prescribe naltrexone as a part of a comprehensive treatment program to help a person overcome their addiction.

The History of naltrexone

Doctors first created naltrexone in a laboratory in 1963.1 The initial use for naltrexone was in the treatment of opioid addiction by the U.S. Food & Drug Administration (FDA) in 1984.

Over time, animal research studies revealed that Naltrexone also helped to decrease alcohol consumption in those struggling with alcohol addiction. Some of these earlier studies found that administering opioid medications, such as morphine, also increased the amount of alcohol consumption in rats. As a result, researchers began to conclude the opiate system and the reward system associated with drinking alcohol were linked. The FDA approved naltrexone in the treatment of alcohol use disorder in 1994.

Today, oral naltrexone is sold under the brand names ReVia and Depade. Injectable naltrexone is sold as Vivitrol, a 30-day extended-release formation given intramuscularly.

HOW does naltrexone work?

Naltrexone is an opioid antagonist. This means that when a person takes the medication, it blocks the opioid receptors in the brain. The medication doesn’t have as high a liking for the opioid receptor as the medication buprenorphine. However, naltrexone has fewer side effects associated with taking the medication. 1 After taking Naltrexone, because the receptors are blocked, when a person takes opioids or drinks alcohol, they are less likely to experience euphoric effects associated with substance use.

The effects of alcohol on a person’s body can be complex. Multiple systems are involved in creating the euphoria and central nervous-system depressing effects of alcohol. 5 However, the opioid system is one of those found to affect those who drink alcohol.

Naltrexone blocks some of the euphoric effects a person experiences from drinking alcohol.1 Ideally, if a person no longer derives pleasure from drinking alcohol, they will discontinue their use.


A doctor will usually recommend a person start taking naltrexone after they have stopped drinking alcohol for at least three days, but sometimes after at least stopping drinking it for seven days. 1 This decreases the likelihood a person will experience side effects, such as nausea, related to taking naltrexone. However, a person can still take naltrexone if they are actively drinking.

Doctors won’t usually prescribe naltrexone if a person has a medical history of liver problems or is pregnant. People who abuse opioids should not take naltrexone because it will cause rapid detoxification of opioids when taking it. Also, if a doctor thinks that a person may need to take opioids in the next seven days, they should probably not take naltrexone. This is because the opioids will be ineffective in managing their pain as long as the naltrexone is in their system.

Doctors usually recommend taking naltrexone for at least three months to treat alcohol use disorders. However, some people may take naltrexone for anywhere from six months to a year. Also, doctors may recommend a person take naltrexone if they may be at an event in their lives when they are at higher risk for relapse. Examples of these times include:

  • after a personal tragedy
  • after the anniversary of a major life event, such as a divorce or death of a loved one
  • when going on vacation
  • during the holidays

When a person stops taking naltrexone, they won’t usually experience any side effects associated with withdrawal.


Fortunately, naltrexone causes a low incidence of side effects, according to the National Institutes of Health. 1 However, it is possible that a person could experience side effects associated with taking naltrexone.

One of the most common concerns related to taking naltrexone is hepatic or liver failure. Because alcohol abuse has the potential to damage a person’s liver, a doctor must take into consideration how affected a person’s liver may be before prescribing naltrexone.

A person should call their doctor if they suspect they are experiencing side effects of liver disease. These include:
  • Fatigue
  • Light-colored bowel movements
  • Nausea
  • Stomach pain that lasts several days
  • Tea-colored urine
  • Weakness
  • Yellow tinge to the eyes or skin
A person should immediately call their doctor if they experience these side effects. A doctor can perform liver function testing to determine if the liver function may be affected. Fortunately, the liver-related effects associated with using naltrexone are usually reversible if a person experiences problems as a result of taking the medicine. 1

Other potential side effects associated with taking naltrexone include:

  • Anxiety
  • Dizziness
  • Fatigue
  • Headache
  • Nausea
  • Vomiting

Less-common side effects associated with taking naltrexone include diarrhea, muscle pain, problems sleeping, and appetite loss.

Common Misconceptions About Naltrexone

One of the most common misconceptions related to taking naltrexone is that the medication can be the sole treatment for a person struggling with addiction. 1 According to the National Institutes of Health, “Naltrexone’s efficacy is “modest.” Some people may experience very successful effects associated with taking naltrexone while others may have modest to minimal effects. The medication is not intended as a “cure” for alcohol or opioid addiction. Instead, doctors intend it as part of a comprehensive treatment plan that includes counseling, group therapies, and potentially other alternative treatments, such as meditation and physical activity.

Another misconception and also commonly unknown fact about naltrexone is that it affects a person’s ability to tolerate using heroin. A person is more likely to experience a heroin overdose if they are using heroin and taking naltrexone. The effects of taking both naltrexone and other medications, such as opioids, can be very unpredictable and potentially dangerous.

How Effective Is Naltrexone?

Several research studies have attempted to determine how effective naltrexone is in treating alcohol use disorders. One such example is a meta-analysis published in 2004. 1 In this analysis of available research regarding the use of naltrexone in treating alcohol disorders, it found that naltrexone was more effective than a placebo in short-term addiction treatment of 12 weeks or less.

Other benefits of short-term naltrexone use included:

  • Longer times before relapse
  • Lower rates of drinking days
  • Fewer drinks per day when a person did drink
  • More days of drinking abstinence
  • Reduced amounts of alcohol consumption while a person is receiving treatments

According to the meta-analysis, taking medications like naltrexone could make the difference between a small slip-up and a total relapse for those who struggle with alcohol abuse.

One of the struggles for those who abuse alcohol is that complete abstinence may not be possible as a treatment for a drinking problem. 5 This is one of the reasons why naltrexone may be effective in treating a drinking problem because taking naltrexone has been shown to reduce the amount a person drinks. If a person can drink in lower quantities, they are ideally more likely to achieve abstinence or experience fewer side effects related to their alcohol abuse.

Another large scale Russian study found that extended-release naltrexone was effective in opioid abstinence treatments. 4 According to the research study, those who were treated with extended-release naltrexone were significantly more likely to be abstinent from opioids than when compared to those who took a placebo. According to the National Institute on Drug Abuse, extended-release naltrexone may be as effective as taking buprenorphine/naloxone (Suboxone) in those who are abstinent from drugs.

Where Can A Person Find More Information About Naltrexone?

If a person struggles with alcohol addiction, they should talk to their doctor about taking Naltrexone and if it could benefit them. Because naltrexone is not associated with causing significant side effects, doctors may be more inclined to prescribe the medication. It also does not require the frequent monitoring that other medications to prevent opioid relapse, such as Suboxone or methadone, do. 5