Abstract red and pink image illustrating an extended release naltrexone for substance use disorder.

Extended Release Naltrexone

Why ER Naltrexone can be a viable option.

Mohammed Rezai DO

Mohammed Rezai DO

Medical Director

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Most people who are familiar with naltrexone take this medication once or twice daily. The extended-release version of naltrexone serves the same purpose, but only needs to be administered once per month. Both the standard form of naltrexone and the extended-release option are recommended as part of a medication-assisted treatment program (MAT). MAT programs are recommended for individuals struggling with substance use disorders. A main component of medication-assisted treatment is prescriptions that assist in managing cravings related to certain substances to encourage recovery. But an equally important (and often lesser-known) portion of MAT is behavior therapies such as counseling and skill building. These talk-based therapy interventions assist with creating and maintaining healthy habits that support a person’s recovery from substance use disorder.

Depending on the type of substance someone is recovering from, doctors will recommend various medications. One of these is extended-release naltrexone, which is approved by the Food and Drug Administration (FDA) for the treatment of alcohol and opioid use disorders. Naltrexone is usually prescribed as a tablet to be taken orally, as this is the standard form this medication comes in. However, extended-release naltrexone is a different type of the same drug that is better-suited for people who struggle with remembering to take a pill regularly.

Why is extended-release naltrexone prescribed?

Individuals take naltrexone, also known by the brand names Vivitrol and Revia, in order to minimize cravings for opioids and alcohol. This medication is part of a comprehensive treatment program that helps someone achieve recovery from these substances. A major advantage of extended-release naltrexone is that it can be administered by any healthcare provider who is qualified and licensed to administer prescriptions. This makes it more readily available than other medications that are part of MAT programs. While there are other factors that can impact compliance within MAT, this medication helps remove a major barrier to recovery: limited access to resources and treatment

What are the effects of extended-release naltrexone?

Due to containing the same active ingredients, extended-release naltrexone and standard naltrexone have a very similar effect on the body. Extended-release naltrexone binds to specific areas in the brain called opioid receptors. This prevents any other substances from entering such areas and, therefore, hinders the effects of recreational opioids and alcohol. As a result, the brain does not respond to alcohol, codeine, heroin, and morphine with its typical sense of euphoria. The idea behind this is to prevent someone from using these substances by eliminating the “high” that results. When the brain registers that there is extended-release naltrexone on opioid receptors, it also does not produce a craving for opiates and alcohol like it usually would for someone who is addicted to these substances.

As its name implies, extended-release naltrexone remains in the body for a longer period of time than standard naltrexone does. This means that it only needs to be taken once per month in order to remain effective in minimizing cravings and reducing drug-related feelings of euphoria. Additionally, extended-release naltrexone is considered safer than other medications used as part of MAT programs. There is no potential for addiction to extended-release naltrexone as it does not produce a high that some individuals may become conditioned to.

Some medications that are part of MAT programs are purposefully and scientifically used alongside other prescriptions. This is done to maximize their effectiveness and minimize cravings for a wider range of substances. However, this is not the case with extended-release naltrexone, as it is intended to be used in isolation.

Anyone taking extended-release naltrexone should avoid substances (both legal and illicit) that can interact negatively with its mechanism of action. This includes alcohol, opioids, sedatives, tranquilizers, and other drugs that have the potential to cause lethargy or fatigue. You should also consult your physician regarding all medications you are on to ensure that there are no negative interactions that will pose a safety risk. When someone combines medications with similar mechanisms, the two substances become doubly powerful and extremely dangerous. In the case of extended-release naltrexone and other sedative-like substances, someone taking both is at risk for excessively slow breathing, a drop in heart rate, coma, and even death.

What forms can extended-release naltrexone be taken in?

Extended-release naltrexone only comes in the form of an injection, which is given in the buttocks via a needle. Since this is not a pill, individuals need assistance from a qualified healthcare provider in order to administer it. Someone taking extended-release naltrexone will need to go to the outpatient clinic where they are receiving other services once per month to receive their injection.

Extended-release naltrexone is also considered to be slightly more effective due to the way it is administered. When naltrexone and other medications are taken by mouth, they must pass through the entire digestive system and get processed by the liver before being released into the bloodstream. By the time this occurs, much of the medication will have been excreted from the body as waste. When most medications are injected, they enter the bloodstream directly and are more quickly available for utilization by the body. But, in the case of long-acting substances such as extended-release naltrexone, the effects are greater than those of an oral tablet and they last over the course of several weeks.

What are the side effects of extended-release naltrexone?

The side effects of extended-release naltrexone are very similar to those associated with standard naltrexone. Some are common and may cause little to no discomfort, while others need to be addressed immediately for someone’s safety. If someone experiences symptoms of an allergic reaction, they most often require hospitalization and close monitoring. Either way, be sure to tell your doctor about how you respond to extended-release naltrexone, since they may be able to make adjustments or recommendations to help. Common side effects of extended-release naltrexone that are not usually a cause for concern include:

  • Nausea
  • Tooth pain
  • Dizziness
  • Vomiting
  • Restlessness
  • Joint pain
  • Stiffness of the joints or muscles
  • Sinus congestion
  • Muscle spasms
  • Fatigue
  • Insomnia
  • Muscle pain or cramps
  • Cold symptoms (runny nose, sneezing, sore throat, and/or cough)
  • Loss of appetite
  • Headache
  • Anxiety

People may also experience some side effects that impact the buttocks, which is the site where the injection is given:

  • Swelling
  • Redness
  • Itching
  • Pain
  • Foul-smelling, white discharge
  • Bruising
  • If there are any issues with the skin surrounding the injection site that do not resolve within two weeks, you will need to see your doctor to treat what may be an infection. Infections must be addressed quickly, as they can easily spread to other parts of the body and lead to death. Your doctor may refer you to a surgeon if you have major skin changes to this area that remain after two weeks.

There are additional side effects, which are rarer and more serious. If any of these result, you should contact your doctor immediately. They may point to an allergic reaction or stem from an underlying medical condition that interacts negatively with this medication:

  • Blisters on the buttocks
  • Major mood changes
  • Suicidal thoughts
  • A fast or irregular heartbeat
  • Chest pain
  • Difficulty breathing
  • Wheezing

Is there anyone who shouldn’t take extended-release naltrexone?

Extended-release naltrexone can cause liver problems, so it’s not recommended to take this medication if you have existing issues related to the liver. People who are currently addicted to, withdrawing from, or have used opioids and/or alcohol in the last two weeks should not take extended-release naltrexone. If you are recently overcoming a minor illness for which you have taken cold medicine, cough medicine, diarrhea medication, and/or pain medication, you should wait at least seven days before taking extended-release naltrexone.

If you think extended-release naltrexone is a good fit for you and want to learn more about whether it can help your opioid use disorder or alcohol use disorder, contact your doctor or a licensed mental health professional. After completing a thorough assessment, they can make recommendations regarding what’s best for your recovery.

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Brittany Ferri PhD

Brittany Ferri PhD

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