If you’re taking naltrexone for opioid or alcohol abuse, you’re probably worried about the side effects of stopping the medication abruptly.

You might have heard about naltrexone withdrawal symptoms and how unpleasant they can be.

In this article, we’ll explain how and why naltrexone withdrawal occurs and what you can do to avoid it.

What Is Naltrexone?

Naltrexone is an FDA-approved prescription medication used to treat substance abuse disorders such as opioid use disorder (opioid addiction) and alcohol use disorder.

Most rehab centers and treatment facilities provide naltrexone as part of their MAT programs  (medication-assisted treatment programs) for treating opioid dependence.

Naltrexone can be taken as an intramuscular injection or as an oral pill. The oral form is used for both opioid and alcohol use disorders, while the injection only works for opioid addiction.

Oral naltrexone treatment is taken daily, while the injectable form of naltrexone is usually taken once a month because of its long-lasting effects.

How Does Naltrexone Work?

Despite what many people think, naltrexone isn’t an opioid but an opioid antagonist. Naltrexone works by blocking the opioid receptors in your central nervous system (brain and spinal cord), so when you take opioid recreational drugs, they don’t work.

Patients with opioid or alcohol dependence are addicted to the euphoric effects of these substances. As an opioid blocker, naltrexone blocks the opioids from producing this euphoric effect, so you start craving them less. It also works for alcohol cravings, but the mechanism is unknown.

What Is Naltrexone Withdrawal?

Most patients taking naltrexone believe that they’ll experience severe opioid withdrawal symptoms if they stop taking it at any point.

However, it’s important to remember that naltrexone isn’t an opioid. That means you can’t become addicted to naltrexone or build up tolerance or dependence on the medication.

Naltrexone withdrawal symptoms don’t occur because you stopped taking naltrexone but instead, because you stopped taking it while you still had opioids in your system.

Whenever you have both naltrexone and opioid analgesics in your system at the same time, you’re more likely to experience what you would call naltrexone withdrawal symptoms. The symptoms are the result of these drug interactions, not the naltrexone.

That’s why most healthcare providers recommend that you fully detoxify your body from all opioids before you start taking naltrexone. You’ll typically need to wait seven to ten days after your last dose of opioids.

Naltrexone Withdrawal Timeline

Naltrexone’s withdrawal timeline depends on how much opioid medication you’ve taken or how much is in your system when you start taking naltrexone.

For example, if you stop taking opioids without naltrexone, it would typically take 12 to 30 hours for your body to start showing withdrawal signs.

However, with naltrexone, the withdrawal symptoms could kick in immediately. The more opioids in your system, especially illicit opioids such as heroin and fentanyl, the stronger the naltrexone withdrawal symptoms are.

Naltrexone Withdrawal Symptoms

While naltrexone doesn’t cause opioid withdrawal symptoms, it can precipitate the following symptoms in patients taking opioids:

  • Fast heart rate (tachycardia)
  • Nausea and vomiting
  • Gastrointestinal problems such as diarrhea and abdominal pain
  • Muscle pain and spasms
  • Agitation and excitability
  • Teary eyes
  • Excessive sweating


Naltrexone withdrawal is only a problem if you have opioids in your system. It can be prolonged if you have liver disease or kidney disease, because the body needs a longer time to fully detoxify.

As long as you’re opioid-free and sticking to your treatment program, you don’t have to worry about any unpleasant withdrawal symptoms.

Naltrexone Withdrawal FAQs

Do I Need to Detox from Naltrexone?

Since naltrexone isn’t an opioid, you don’t need to detoxify from it. However, you should consult with your healthcare provider before you stop taking the medication altogether because you might still require naltrexone.

Is Naltrexone A Cure for Addiction?

Naltrexone isn’t a cure for addiction. However, it’s a vital part of most opioid addiction programs, which include medication and behavioral counseling. Naltrexone reduces your cravings, so you have a better chance of sticking to your treatment program and not relapsing.

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