What Is Naltrexone?
Naltrexone is an opioid receptor antagonist, which means it occupies the opioid receptors of the brain, blocking the activity of opioids. It blocks both the euphoric and sedative effects of opioids and is used in the treatment of alcohol use disorder and opioid dependence.
Naltrexone is available in two forms:
- An extended-release injectable, called VivitrolⓇ
- A pill, called ReviaⓇ, also called naltrexone hydrochloride
FDA Approval of Naltrexone
The U.S. Food and Drug Administration (FDA) approves the use of naltrexone in the treatment of:
- Alcohol dependence, approved in 1984
- Opioid dependence, approved in 1994
Many people may struggle with both opioid and alcohol abuse. This is a dangerous combination that should be actively managed. The good news is that naltrexone can be used to treat both opioid and alcohol dependence.
Naltrexone for Alcohol Addiction
Even though naltrexone works on the brain’s opioid receptors, it is effective in the treatment of alcohol abuse. This is because alcohol also acts on the internal opioid and endorphin system.
A meta-analysis study showed that naltrexone was successful in reducing both the quantity of alcohol consumption and the degree of perceived craving.
Naltrexone for Opioid Addiction
Naltrexone acts to bind opioid receptors without activating them. In clogging up the receptors, naltrexone prevents the action of opioids and thus the high associated with their use.
Naltrexone works to ease the immediate physiological changes, such as euphoria and decreased breathing, as well as the delayed disturbances of cravings and the urge to use opioids. In doing so, naltrexone works to treat opioid dependence in preventing the desire to use the drugs.
Dosage and Administration
The oral version of naltrexone, called ReviaⓇ, can be taken with or without food. The FDA recommends long-term therapy (longer than three months) as the most effective for both the oral and injectable formulations. Therapy may also be used indefinitely if needed. The recommended dosage of naltrexone should be administered by a medical professional and may vary for each patient. Typical dosages are:
Oral Naltrexone (Revia)
- Alcohol Dependence
50 mg* / day
- Opioid Dependence
25 – 50 mg* / day
Intramuscular Naltrexone (Vivitrol)
- Alcohol dependence
380 mg injection once-monthly
- Opioid dependence
380 mg injection once-monthly
Individuals who need to undergo laboratory tests should inform their doctor or laboratory personnel that they are taking oral naltrexone. This medication may interfere with certain laboratory tests (including drug tests).
*As naltrexone is broken down in the liver and kidneys, people with preexisting liver or kidney conditions may require an adjusted dose. Additionally, people on certain medications may require alterations in their dosage. Always consult a physician before commencing or changing a prescribed medication.
There are a few different ways in which naltrexone works to treat opioid and alcohol addiction. The therapeutic effects produced by naltrexone work by:
- Blocking the effects of opioids
- Decreasing the desire and urge to use opioids and alcohol
- Increasing self-control and ability to refrain from using opioids and alcohol
Although they have a similar name, naloxone and naltrexone are not the same. Naltrexone is used in the treatment of opioid addiction to prevent the physiological and psychological effects of opioids. Naloxone, on the other hand, is used in response to an overdose, after a toxic quantity of opioids is consumed. The brand name for naloxone is NarcanⓇ.
Methadone is an opioid agonist, meaning it activates opioid receptors. This is in comparison to naltrexone, which acts to bind opioid receptors but not activate them (an antagonist).
Precautions should be taken when switching from one medication to another, as a period of abstinence is often required. As always, consult your physician before making any changes to your prescribed regimen.
Naltrexone Drug Interactions
Naltrexone does interact with other medications.
All forms of opioids, or medications containing an opioid, should be avoided while taking naltrexone. Naltrexone may reduce tolerance, inadvertently causing serious side effects. Taking naltrexone may make you more sensitive to opioids in the future. This is particularly important in regards to the injectable form of naltrexone.
Taking naltrexone with opiates in your system is dangerous and should not be attempted.
Disulfiram should not be taken in combination with naltrexone, as both can be harmful to the liver.
The following medications should be avoided:
- Opiates, including codeine and hydrocodone
- Cough medications, including dextromethorphan
- Diarrhea medications, including diphenoxylate
If you have any questions or concerns about potential drug interactions, speak with your doctor.
Naltrexone Side Effects
Like many medications, naltrexone does have side effects. Thankfully though, many people tolerate naltrexone well.
Common side effects include:
- Abdominal cramping
- Fatigue and lethargy
- Difficulty sleeping
- Joint and muscle aches
- Nervousness or anxiety
Rare side effects include:
- Suicidal ideation
- Elevated liver enzymes
- Skin rash
- Dry mouth
Naltrexone should be used with prudence. Certain individuals may become sensitive to even low dose opioids while taking naltrexone. Naltrexone warning: This sensitivity combined with a previously tolerated dose of opioids may lead to life-threatening intoxication.
Individuals should also take precautions when switching from one medication to another, as a period of medication abstinence may be required beforehand. As always, consult your physician before making any changes to your prescribed regimen.
- Precipitated Withdrawal
Naltrexone does not produce tolerance or withdrawal symptoms itself. In plugging up the opioid receptors, it may produce withdrawal symptoms in someone who is dependent on opioids. This is due to the fact that opioids can no longer access the receptors (blocked by the action of naltrexone). This can be the case for people have used naltrexone for both a long or short time. A similar process occurs in alcohol dependence.
This is why it is imperative to allow for an opioid-free period of 7 to 10 days before starting naltrexone. This opioid-free period prevents precipitating withdrawal.
- Naltrexone During Pregnancy
Naltrexone use during pregnancy is a delicate matter. While naltrexone has potential in the treatment for opioid-dependent pregnant women, its current uses are limited, as little data exists on its safety profile in humans.
Naltrexone is classified as a Category C medication, which means that animal reproduction studies have shown adverse effects on a developing fetus. As of now, there are no equivalent studies in humans. What is well known, however, is the direct and detrimental effects of opioids, such as heroin, on a developing fetus. Opioid and alcohol use during pregnancy should be strictly avoided.
If someone becomes pregnant while prescribed naltrexone, they should discontinue taking the medication if the risk of opioid-relapse is low. If the risk of relapse is believed to be high, a physician may decide that continued naltrexone use is warranted. In this case, the good may outweigh the bad. Some studies have demonstrated favorable outcomes using naltrexone for people who have used opioids heavily. Naltrexone may provide the support needed to ensure an opioid-free pregnancy, and as a result, a healthy baby.
Additionally, naltrexone and its metabolites are found in breast milk, a consideration all breast-feeding mothers should discuss with their doctors. It is important to consult your physician if you become pregnant while taking naltrexone.
- Naltrexone Overdose Risk
It is not possible to overdose on naltrexone alone. This is because although naltrexone binds opioid receptors, it does not activate them. It should be noted, though, that excessive amounts of opioids may displace the naltrexone medication from the opioid receptors. This increases the risk of harmful intoxication such as respiratory arrest and/or circulatory collapse.
Talking immoderate amounts of opioids in an attempt to overcome the effects of naltrexone is exceptionally dangerous and should never be attempted.
- Liver or Kidney Disease Risk
Naltrexone is broken down in the liver and excreted through the kidneys. As naltrexone is metabolized in the liver and kidney, there exists some risk. People on naltrexone should have their liver function tests monitored, both before taking the medication and periodically during their regimen.
- Naltrexone Black Box Warning
Some people may experience inflammation of the liver, known as hepatitis, with high doses of naltrexone. Naltrexone is contraindicated in acute hepatitis or liver failure. People with pre-existing liver conditions may need alterations in their dosing regimens to prevent liver injury.
Although there are no specific recommendations in individuals with kidney impairment, it should be used with caution as the byproduct of naltrexone is excreted in urine. It is not necessary to monitor kidney function while taking naltrexone.
Naltrexone Use Statistics
Overall, naltrexone has demonstrated its usefulness in treating opioid dependence and has helped many people treat opioid addiction. Here are a few statistics highlighting the potential for naltrexone in aiding in the treatment of opioid dependence.
- The percentage of opioid treatment programs offering naltrexone increased from 11 percent in 2011 to 25 percent in 2015. The trend continues to increase in 2019.
- Naltrexone has been shown to decrease drinking days by 25%.
- Using opioid antagonists like naltrexone led to fewer drinking days, lower rates of resumed heavy drinking, and reduced alcohol cravings
Key Points: Understanding Naltrexone Treatment & Your Recovery
Naltrexone is used in the treatment of opioid and alcohol dependence and is prescribed as part of a comprehensive treatment plan that includes behavioral therapy and social support programs. Some key points about naltrexone include:
- Naltrexone has been shown to reduce the quantity of alcohol consumption
- Naltrexone has been shown to reduce the severity of cravings and urges
- Naltrexone improves relapse rates and duration of abstinence for many patients
- Naltrexone has a relatively safe side effect profile, with a black-box warning stating the potential of liver damage at high doses
The Recovery Village Palm Beach at Baptist Health offers several treatment plans for opioid addiction and other substance use disorders. If you or a loved one are dealing with a substance use disorder and would like help, please call today to get started on the road to recovery.
Alderks, Cathie. “Buprenorphine, and Extended-Release Naltrexone at Substance Abuse Treatment Facilities: 2003-2015 (Update)”. Substance Abuse and Mental Health Services Administration, August 22 2017. Accessed August 8 2019.
Comer, Sandra; Sullivan, Maria; et al. “Injectable, Sustained-Release Naltrexone for the Treatment of Opioid Dependence: A Randomized, Placebo-Controlled Trial”. Arch Gen Psychiatry, February 2006. Accessed 18 July 2019.
Garbutt, James; Kranzler, Henry; et al. “Efficacy and Tolerability of Long-Acting injectable Naltrexone for Alcohol Dependence: A Randomized Controlled Trial.” Journal of the American Medical Association, April 6 2005. Accessed 17 July, 2019.
Gonzalez, John; Brogden, Rex. “Naltrexone: A Review of its Pharmacodynamic and Pharmacokinetic Properties and Therapeutic Efficacy in the Management of Opioid Dependence.” Drugs, March 1988. Accessed 17 July 2019.
Hendershot, Christian; Wardell, Jeffrey; et al. “Effects of Naltrexone on Alcohol Self-Administration and Craving: Meta-Analysis of Human Laboratory Studies.” Journal of Addiction Biology, 14 July 2016. Accessed 17 July 2019.
Hulse, Gary; O’Neil, George; Arnold-Reed, Diane. “Methadone Maintenance Versus Implantable Naltrexone Treatment in the Pregnant Heroin User”. International Journal of Gynecology and Obstetrics, 2004. Accessed August 6, 2019.
Johansson, Bjorn Axel; Berglund, Mats; Lindgren, Anna. “Efficacy of Maintenance Treatment with Naltrexone for Opioid Dependence: a Meta-Analytical Review. Journal of Addiction, 14 February 2006. Accessed 17 July 2019.
Kranzler, Henry; Van Kirk, Jeffery. “Efficacy of Naltrexone and Acamprosate for Alcoholism Treatment: A Meta-Analysis.” Alcoholism, Clinical & Experimental Research, 11 April 2006. Accessed 17 July 2019.
Kranzler, Henry; Wesson, Donald; et al. “Naltrexone Depot for Treatment of Alcohol Dependence: A Multicenter, Randomized, Placebo-Controlled Clinical Trial.” Alcoholism, Clinical Experimental Research, 3 May 2006. Accessed 17 July 2019.
National Centre for Biotechnology Information. “Incorporating Alcohol Pharmacotherapies Into Medical Practice: A Treatment Improvement Protocol Series, No. 49”. U.S. Department of Health and Human Services. Centre for Substance Abuse Treatment, 2009. Accessed July 19th, 2019.
O’Malley, Stephanie. “Opioid Antagonists in the Treatment of Alcohol Dependence: Clinical Efficacy and Prevention of Relapse.” Yale University, 25 September 1995. Accessed 17 July 2019.
Saia, Kelley; Schiff, Davida; et al. “Caring For Pregnant Women with Opioid Use Disorder in the USA: Expanding and Improving Treatment”. Current Obstetrics and Gynecology Reports, September 2016. 5(3), 257-263. Accessed 18 July 2019.
Xuei, X; Dick, D; et al. “Association of the K-Opioid System with Alcohol Dependence”. Molecular Psychiatry, November 2006. Accessed 19 July 2019.
Medical Disclaimer: The Recovery Village aims to improve the quality of life for people struggling with a substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare provider.