The Basics of Naltrexone
This article focuses primarily on oral naltrexone tablets. However, the same active ingredient is also available as a long-acting injection (Vivitrol) that people receive on a monthly basis. Both forms of naltrexone provide essential treatment for AUD.[1]
This chart outlines the history and basics of naltrexone:[1-3]
| What It Is Used For | Reducing alcohol cravings and the risk of heaving drinking episodes in individuals with alcohol use disorder |
| Invention | Discovered in 1963 |
| FDA Approval | Oral form approved in 1984, and injectable form approved in 2006 |
| Dose | 50 mg oral tablets |
| Frequency of Use | Oral tablets taken once daily |
| Other Forms | An extended-release monthly injection (Vivitrol) |
How Effective Is Naltrexone for Alcohol Use Disorder?
Research demonstrates naltrexone’s effectiveness in treating AUD. Studies indicate that when combined with therapy, naltrexone can aid in the following:
- Reducing heavy drinking days: Individuals taking naltrexone experience fewer heavy drinking days compared to those taking a placebo.[1]
- Decreasing alcohol cravings: Naltrexone helps to diminish the desire to drink, making it easier to control alcohol intake.
- Improving overall recovery outcomes: Overall, naltrexone contributes to longer periods of abstinence from alcohol and better long-term treatment outcomes.[2]
For medications like naltrexone to be most effective, they must be combined with behavioral therapies as part of a comprehensive treatment program. Medication alone does not treat the underlying causes of a substance use disorder. However, it can assist people in maintaining sobriety, so they are better able to fully engage in meaningful therapies.
How Does Naltrexone Work?
Naltrexone is an opioid antagonist. It works by blocking the pleasurable effects of alcohol on opioid receptors in the brain.[2]
When someone who is taking naltrexone drinks alcohol, they don’t experience the usual reward sensation associated with drinking. This helps to reduce motivation to drink and decreases the reinforcing effects of alcohol.[3]
Naltrexone may be started during the withdrawal period, but it is more commonly prescribed after detox to help with ongoing relapse prevention.[4]
Side Effects of Naltrexone
While generally considered safe, naltrexone can cause side effects. Most side effects are mild and subside over time.
Common side effects of Naltrexone include the following:[3]
- Nausea and vomiting
- Stomach aches or cramps
- Diarrhea
- Constipation
- Loss of appetite
- Headaches
- Dizziness
- Anxiety and nervousness
- Irritability
- Tearfulness
- Difficulty falling or staying asleep
- Increased or decreased energy
- Muscle or joint pain
- Drowsiness
- Rash
If any of the above side effects become severe or do not go away, contact your healthcare provider. Serious side effects that require immediate attention include the following:[5]
- Confusion
- Hallucinations
- Blurred vision
- Severe vomiting or diarrhea
Taking Naltrexone
Naltrexone should be taken exactly as instructed by your doctor. If you miss a dose, take it as soon as you remember it unless you are close to taking your next regular dose. It is not safe to take a double dose to make up for a missed one. Naltrexone remains in your system for many hours.[3]
Naltrexone has a half-life of approximately four hours. The active metabolite is about 13 hours.[6] This means significant levels remain in your system for several hours after taking a dose.
The time that naltrexone stays active in your system may be slightly longer than the half-life. Naltrexone is most effective when taken as prescribed, so follow your prescribing doctor’s guidelines.
Who Is Not a Candidate for Naltrexone?
Naltrexone may not be suitable for everyone. Certain people may experience adverse side effects if they take the medication.
Naltrexone is not recommended for individuals who meet any of these criteria:[2,7]
- Are currently using opioids or have a recent history of opioid dependence
- Have severe liver or kidney disease
- Are allergic to naltrexone
- Are pregnant or plan to become pregnant
- Taking other medications that may interact with naltrexone
FAQs
These are some of the questions we hear most about using naltrexone:
Naltrexone is primarily available as an oral tablet. It is obtained via prescription, and users are responsible for taking their doses on schedule at home. The injectable form (Vivitrol) is only given by trained healthcare professionals, and the dose lasts about a month.
Naltrexone is not directly associated with weight gain.[8]
Naltrexone is not classified as a controlled substance. It is also not addictive.
Naltrexone is generally not recommended for those with liver issues. Individuals with existing kidney problems should use naltrexone with caution, and discuss alternative options with their doctor.
- Maisel, N., Blodgett, J., Wilbourne, P., Humphreys, K., Finney, J. Meta-analysis of naltrexone and acamprosate for treating alcohol use disorders: When are these medications most effective? Addiction. 2013;108(2):275-293.
- Naltrexone. Substance Abuse and Mental Health Services Administration. Published January 30, 2024. Accessed March 28, 2024.
- Roos CR, Bold KW, Witkiewitz K, et al. Reward drinking and naltrexone treatment response among young adult heavy drinkers. Addiction. 2021;116(9):2360-2371.
- Sigmon SC, Bisaga A, Nunes EV, O’Connor PG, Kosten T, Woody G. Opioid detoxification and naltrexone induction strategies: Recommendations for clinical practice. The American Journal of Drug and Alcohol Abuse. 2012;38(3):187-199.
- Naltrexone. U.S. National Library of Medicine. Published October 15, 2017. Accessed March 28, 2024.
- Singh D, Saadabadi A. Naltrexone. StatPearls. Published 2020.
- Ayyala D, Bottyan T, Tien C, et al. Naltrexone for alcohol use disorder: Hepatic safety in patients with and without liver disease. Hepatology Communications. 2022;6(12).
- Tek C, Ratliff J, Reutenauer E, Ganguli R, O’Malley SS. A randomized, double-blind, placebo-controlled pilot study of naltrexone to counteract antipsychotic-associated weight gain. Journal of Clinical Psychopharmacology. 2014;34(5):608-612.
