Stethoscope on peach background. Naltrexone side effects

What are the Side Effects of Naltrexone?

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Naltrexone can be an important part of recovery, but you should also be aware of possible side effects.

For many people in recovery, medically assisted treatment can be far more effective than traditional therapy alone. Naltrexone is part of medically assisted treatment for some who are recovering from alcohol or opioid use. For those struggling to manage their drinking or stop entirely, naltrexone can reduce alcohol cravings, which makes it easier to limit drinks. For people who are fully detoxed from opioids and in stable recovery, it can diminish cravings and lessen the chance of a slip. This all sounds great, right? But like any medication, there are also side effects to consider. 

Before we dive into the side effects, please note that this post is intended for informational use only, and does not replace medical care! If you have concerns about the side effects of naltrexone, please speak with your doctor. 

Naltrexone is either taken daily in pill form or injected once a month as Vivitrol. For most people, the side effects of naltrexone are mild. They also usually diminish or go away completely as the body adjusts to the medication. 

Here are some of the common side effects of naltrexone:

  • Trouble sleeping
  • Joint and muscle pains
  • Headache
  • Abdominal pain and cramps (sometimes with diarrhea or constipation)
  • Nausea and vomiting
  • Tiredness
  • Dizziness
  • Delayed ejaculation

In the majority of people prescribed naltrexone, the side effects listed above are pretty mild. For them, the benefits of incorporating naltrexone into their recovery usually make the discomfort worth it. Especially since these side effects don’t last that long for most people. But what if you’re in the minority of people who experience uncommon, more serious side effects?

Rarely, people experience these more severe side effects of naltrexone:

  • Chest pain
  • Confusion
  • Severe abdominal or stomach pain
  • Blurred vision with aching, burning, or swollen eyes
  • Discomfort while urinating or frequent urination
  • Fever
  • Ringing or buzzing in the ears
  • Shortness of breath
  • Hallucinations
  • Depression or other mood or mental changes
  • Swelling in the face, feet, or lower legs
  • Itching
  • Weight gain

If you experience any of the more serious side effects listed above, talk to your doctor or pharmacist. 

There are a few other issues that can arise with naltrexone that you should be aware of. These are not side effects but are important health considerations

Other health considerations for naltrexone:

  • Opioid withdrawal – Because naltrexone blocks the effects of opioids, it’s important to have no opioids in your system. We recommend a minimum of 7-10 days with no opioid use before starting on naltrexone. If you are using opioids when you begin taking naltrexone, it can drop you right into opioid withdrawal. And that’s not fun!
  • Risk of liver damage – Naltrexone carries the risk of problems with your liver. For those of us who have spent years abusing our livers with other substances, it’s important to be aware of! If you start having dark urine, pain in your upper stomach, or yellowing of your eyes or skin while taking naltrexone, contact your doctor right away. If you already have hepatitis or liver problems, tell your doctor before taking naltrexone.
  • Risk of opioid overdose – There are two key dangers here. First, as previously mentioned, naltrexone blocks the effects of opioids. So if someone relapses while taking naltrexone, they may take a larger dose of opioids than usual to try to overcome that block, leading to overdose. The other danger occurs if someone stops taking naltrexone, and resumes using opioids. Having taken naltrexone can make a person more sensitive to opioids. So if they resume using opioids at their previous dose (or even a lower dose), it can be too much for their new, reduced tolerance.  

I know, that all sounded pretty scary! But the truth is, serious side effects of naltrexone are rare, and most people tolerate it quite well. Either way, it is much safer to be fully informed when you decide on a treatment plan than to be optimistic but ignorant. Now that you know the side effects, you know what to expect and what to be on the lookout for. 


This blog post has been reviewed for medical accuracy by Paul Leonard, MD.

Alaine Sepulveda is a content strategist in recovery from alcohol. She believes that engaging people and sharing stories with them allows us to spread knowledge, and to help others in the path to recovery. She holds an MA in Communication Studies from New Mexico State University.

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