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Naltrexone Side Effects: Is It Worth the Risk?

Naltrexone is a medication used for its ability to block the effects of opioids like heroin, valium, and codeine as well as alcohol. The most notable side effects associated with naltrexone include nausea, dizziness, drowsiness, and headaches.

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What Is Naltrexone?

Naltrexone is a non-narcotic that works by effectively blocking the effects of narcotics. 

The medication helps to prevent euphoric feelings associated with alcohol and opioids that drug users most often seek. Naltrexone is most commonly used in the treatment of heroin and alcohol use disorders.

Naltrexone is approved by the FDA for medication-assisted treatment (MAT). It does not produce any narcotic-like effects, which helps those who use it avoid substance abuse.

Naltrexone & Addiction Treatment

Think back to your first drink or your first drug experience. Remember that feel-good sensation that took hold? The high (or the memory of it) keeps you returning to drugs. Naltrexone can break the cycle. 

Researchers say naltrexone can accomplish three things:

  1. Reduce cravings: You won’t feel compelled to return to using or drinking. 
  2. Sobriety: Since you can resist your cravings, you’re less likely to relapse.
  3. Blocking: Naltrexone can stop a high if you slip and drink or use drugs. 

Most people take naltrexone for 12 weeks or more. Your doctor might give you pills you take every day. Or if you’re worried you’ll skip pills so you can relapse, a long-lasting injection may be a better option. 

Naltrexone Common Side Effects

Side effects associated with naltrexone include the following:

  • Vomiting
  • Joint pain
  • Muscle pain
  • Loss of appetite
  • Sleep disorders
  • Symptoms of a cold
  • Tooth pain

Another notable effect of naltrexone is that it subdues or blocks the effects of alcohol and narcotics. Some individuals take naltrexone and then try to cancel out its effects by consuming more alcohol or controlled substances. Such an approach can result in increased intoxication, serious injury, bodily harm, coma, or even death.

Naltrexone should never be used recreationally. It will not produce euphoria or a high, so there is little point in attempting to abuse it. It is only intended for the treatment of alcohol and opioid abuse.

Serious Side Effects of Naltrexone

When naltrexone is taken as an injection, side effects can occur at the site of the injection. Intense pain or tissue damage can occur. The area can also swell, harden, scab, and blister.

Other serious side effects that can occur when taking naltrexone in either injectable or pill form include:

  • Liver damage 
  • Stomach pain
  • Jaundice
  • Darkened urine
  • Respiratory issues
  • Pneumonia 
  • Depression

Naltrexone works by binding and blocking the brain’s opioid receptors, which results in reduced and suppressed cravings for opioids. Naltrexone does not cause withdrawal symptoms after quitting use, and there is no potential for abuse or diversion.

Naltrexone Drug Interactions: What You Should Know

How many drugs, medications, and supplements do you use every day? Each one could connect with, block, or augment your naltrexone dose. 

Naltrexone can interact with the following substances:

  • Opioids: Do you take painkillers for a chronic condition? Your next dose of naltrexone will block them from their receptors, pushing you into immediate withdrawal. Naltrexone will also (obviously) keep your next dose of illicit drugs from working too.
  • Prescription and over-the-counter medications: Your liver processes naltrexone and many other drugs. More than 315 drugs are known to interact with naltrexone, and most involve liver damage.
  • Alcohol: Some experts encourage people to take naltrexone only on “drinking days” to motivate people to sip and have a bad experience. This approach is an easy way to slip back into addiction.

    If you stop taking naltrexone for several days and then drink, your sip could overpower your changed brain. That big response could be so rewarding that you start drinking again. 

Do not drink or use drugs while taking naltrexone. And talk to your doctor about all the other supplements, vitamins, and prescriptions you take before your therapy begins.

Why Do People Use Naltrexone?

Naltrexone was developed in 1963 and approved for medical use in the United States in 1984. Naltrexone is approved by the FDA for the treatment of both opioid use disorder and alcohol use disorder. 

Individuals use naltrexone to alter the reinforcing effects and euphoric feeling that opioids and alcohol tend to produce. Those who wish to manage their alcohol and/or opioid addictions can utilize naltrexone, which inherently changes the individual’s expectations and relationship with the substance in question. Once the positive effects of the drug are removed, the individual is more likely to abstain from substance abuse.

Risk of Overdose

There is limited data on the toxicity of naltrexone and its potential for overdose. People who have taken 800 mg of naltrexone over the course of seven days reported feelings of depression, suicidal ideation, and respiratory problems.

Animal testing has shown that there is a potential for death due to convulsions and/or respiratory failure, but human testing remains inconclusive currently.

Part of a Full Treatment Approach

Patients using naltrexone should always be medically monitored and have a thorough understanding of this drug and their own relationship to controlled substances before use. Naltrexone use should be supplemented with therapy and rehabilitation to ensure efficacy and reduce the likelihood of relapse.

Simply treating a substance use disorder with medication is not sufficient. It should be used as part of a comprehensive addiction treatment program that includes therapy and social support.

An individual who wants to take naltrexone for the treatment of alcohol use disorder or opioid use disorder will generally have to fill out a naltrexone readiness form that will have the patient go over medical history, drug use, physical exam, lab work, and any additional relevant information to gauge the individual’s readiness to take naltrexone.

Naltrexone is given in either injectable or pill form. Naltrexone in pill form (ReVia, Depade) is taken once per day at 50 mg. Naltrexone in injectable form (Vivitrol) is given once a month at 380 mg. The injectable form of naltrexone is extended-release. 

In most instances, doctors will recommend that you start taking Naltrexone in pill form to ensure you are not having any significant adverse effects. Once this has been established, one may benefit from a monthly injection.

Risk Factors for Adverse Reactions

When used as prescribed, naltrexone is safe and effective. There are no known long-term problems associated with naltrexone use over an extended period of time.

However, allergic reactions can occur when taking naltrexone, which can cause anaphylaxis, which requires immediate medical attention. If you develop a rash, have trouble breathing, or experience swelling in the face, mouth, or tongue, you may be having an allergic reaction to naltrexone. 

Individuals taking naltrexone who relapse may experience a decreased tolerance to alcohol or opioids. Those who are using naltrexone for opioid addiction can experience an overdose if taking their normal amount or even a lesser amount, which can have dire consequences and even result in death.

Studies have shown that there is no evidence of increased risk of adverse events when taking oral naltrexone, meaning that naltrexone has been shown to be safe when compared to a placebo. Any adverse reactions and symptoms should be addressed by medical professionals as soon as possible. 

Is Naltrexone Worth the Risk?

Experts say using naltrexone is safe and effective even over the long term. If you’re using drugs or alcohol and can’t stop, this medication could be critical for you. 

But remember that naltrexone is a prescription medication that should be used with care. Follow your doctor’s instructions carefully, and never start taking the drug without consulting a professional first. 

Naltrexone Side Effects FAQs

Can you overdose on naltrexone?

Naltrexone is not a narcotic, and there are no indications of toxicity unless the individual is allergic to the medication. However, those who treat opioid and/or alcohol use disorders with naltrexone may end up relapsing and experience diminished tolerance, which can result in opioid overdose or alcohol poisoning.

Does naltrexone have any serious side effects?

Minor side effects of naltrexone include nausea and dizziness. Some serious side effects, such as vomiting, muscle and joint pain, and suicidal thoughts, can occur and should be monitored closely. Naltrexone should also be utilized in a monitored medical environment and should never be used recreationally.

Do I have to wait to use naltrexone?

For those with an opioid use disorder, waiting about seven days after the last use of opioids to begin naltrexone will reduce the chances of precipitated withdrawal. If taken too early, precipitated withdrawal can occur, as naltrexone becomes attached to the brain’s opioid receptors.

When should I take naltrexone? Should I take it first thing in the morning or at night?

Naltrexone is generally taken in the morning, though a specific time frame is not specified by manufacturers. Taking naltrexone after breakfast first thing in the morning is a good way to set a schedule so you remember to take your medication.

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Medically Reviewed By Dr. Alison Tarlow

Dr. Alison Tarlow is a Licensed Clinical Psychologist in the States of Florida and Pennsylvania, and a Certified Addictions Professional (CAP). She has been a practicing psychologist for over 15 years. Sh... Read More

Updated October 17, 2023
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