Naltrexone: Definition, How It Works, Uses, Dosage, Effects, Alternatives

Naltrexone is an FDA-approved medication for treating alcohol use disorder and opioid use disorder. It is classified as an opioid antagonist, meaning it blocks the effects of opioids and reduces alcohol cravings.

Naltrexone works by binding to opioid receptors in the brain, preventing opioids from producing euphoria and reducing the reinforcing effects of alcohol. This helps individuals maintain abstinence and lowers the likelihood of relapse.

Naltrexone is primarily used for alcohol dependence and opioid dependence. It is most effective when combined with behavioral interventions and medical management rather than being used as a standalone treatment.

The standard dosage of naltrexone for alcohol use disorder is a 50 mg oral tablet taken once daily. An extended-release injectable form is also available, administered once per month.

Common side effects of naltrexone include nausea, headache, and dizziness. Moderate effects involve increased anxiety or trouble sleeping. Serious side effects, though rare, include liver toxicity and severe allergic reactions.

Alternatives for opioid use disorder include methadone and buprenorphine, which activate opioid receptors rather than block them. For alcohol use disorder, other options include acamprosate and disulfiram, which work differently to help reduce drinking behaviors. According to Anton et al. (2006) in their study “Combined Pharmacotherapies and Behavioral Interventions for Alcohol Dependence: The COMBINE Study,” naltrexone combined with medical management resulted in a 20% reduction in the risk of heavy drinking compared to placebo, with adherence rates ranging from 50.0% to 72.6%, depending on genetic factors.

What Is Naltrexone?

Naltrexone is an opioid antagonist medication used to treat alcohol dependence and opioid use disorder. It works by blocking opioid receptors in the brain, reducing cravings and the pleasurable effects of alcohol and opioids. Unlike opioids, it is non-addictive and does not produce euphoric effects. Common brand names include Revia and Vivitrol.

Naltrexone is primarily used in medication-assisted treatment for alcohol dependence and opioid use disorder. It helps individuals reduce alcohol consumption or maintain abstinence from opioids when combined with counseling and behavioral therapy. Unlike opioid-based treatments such as methadone, it does not lead to physical dependence. According to Jonas et al. (2014) in the study “Pharmacotherapy for Adults With Alcohol Use Disorders in Outpatient Settings: A Systematic Review and Meta-analysis,” treatment with oral naltrexone reduced the risk of heavy drinking by 83% across 50 randomized trials involving 7,793 participants. The same study reported that the number needed to treat (NNT) was 12 to prevent a return to any drinking and 20 to prevent a return to heavy drinking.

How Is Naltrexone Consumed?

Naltrexone is consumed as a daily oral tablet or as a long-acting intramuscular injection to support addiction treatment. The oral tablet, commonly sold under the brand name ReVia, is taken once per day at a standard dose of 50 mg. The injectable form, Vivitrol, is administered once a month by a healthcare provider and requires a 14-day opioid-free period before the first dose. 

Below are the key differences between both forms of naltrexone:

• Oral tablet: Provides flexibility in dosing but requires consistent daily adherence to maintain effectiveness. Missing doses lead to reduced benefits and increased relapse risk.
• Intramuscular injection: This ensures continuous medication delivery for a full month, improving adherence for those struggling with daily pill use. It requires an in-office visit for administration but eliminates the need for daily reminders.

What Is the Chemical Composition of Naltrexone?

The chemical composition of naltrexone is C20H23NO4, which classifies it as a synthetic opioid antagonist. It has a molecular weight of 341.4 g/mol and is structurally similar to oxymorphone but lacks opioid activity. The compound binds to mu-opioid receptors, preventing the reinforcing effects of alcohol and opioids. According to Palpacuer et al. (2017) in the study “Pharmacologically Controlled Drinking in the Treatment of Alcohol Dependence or Alcohol Use Disorders,” naltrexone was found to reduce total alcohol consumption, although no significant health outcome improvements were demonstrated across the analyzed trials.

How Is Naltrexone Made?

Naltrexone is made through a chemical synthesis process that involves modifying noroxymorphone, a derivative of thebaine, to create a high-purity opioid receptor antagonist. The process includes reacting noroxymorphone with cyclopropyl methyl halide in the presence of N-ethyl-2-pyrrolidone at temperatures between 30-100°C. An acid scavenger is used to control unwanted byproducts, ensuring a final product with minimal impurities. According to the European Patent Office document EP2635586B1 (2011) titled “Method for the Manufacturing of Naltrexone,” the final product contains 99.0% pure naltrexone, with impurities such as noroxymorphone kept below 0.1%.

What Is the Mechanism of Action of Naltrexone?

The mechanism of action of naltrexone involves opioid blockade through competitive binding to mu-opioid receptors, preventing opioids from producing euphoric effects. This process alters neurotransmitters by reducing dopamine release, which helps individuals in addiction recovery by decreasing cravings and the reinforcing effects of alcohol and opioids. Naltrexone has a bioavailability of approximately 5-40% when taken orally and a half-life of 4-13 hours, depending on metabolism.

The opioid receptor antagonist effect lasts longer due to the active metabolite 6-beta-naltrexol, which extends receptor blockade for up to 24 hours. According to Palpacuer et al. (2017) in the study “Pharmacologically Controlled Drinking in the Treatment of Alcohol Dependence or Alcohol Use Disorders,” naltrexone reduces alcohol consumption, though its overall health benefits remain an area of further research.

How Is Naltrexone Used in Addiction Rehab?

Naltrexone is used in medication-assisted treatment for opioid addiction and alcohol use disorder to support relapse prevention. In addiction rehab, naltrexone can be administered in two forms: a daily oral tablet or a monthly extended-release intramuscular injection (Vivitrol). The injectable form is especially beneficial for individuals who struggle with daily medication adherence, offering consistent therapeutic levels and reducing the risk of missed doses. Clinical guidelines recommend initiating naltrexone only after the patient has been detoxified and has remained opioid-free for 7 to 10 days to avoid precipitated withdrawal.

Naltrexone’s role in addiction treatment is backed by strong evidence. According to Kranzler and Van Kirk (2001) in the study “Efficacy of Naltrexone and Acamprosate for Alcohol Dependence: A Meta-Analysis of Randomized Controlled Trials,” individuals treated with naltrexone were 17% less likely to relapse and had a 36% greater chance of remaining abstinent compared to placebo. It is not a standalone treatment but is combined with counseling and behavioral therapies in addiction rehab programs. It helps reduce cravings and blocks the euphoric effects of alcohol and opioids, making it a key tool in long-term recovery. 

Is Naltrexone Used During Detox?

No, Naltrexone is not used during detox because it triggers immediate and severe withdrawal symptoms in individuals dependent on opioids or alcohol. Before starting treatment, patients must complete a detox phase to clear opioids or alcohol from their system to avoid severe withdrawal reactions. According to Avery (2022) in the study “Naltrexone and Alcohol Use,” naltrexone requires a period of abstinence before administration, ensuring that it is used safely as part of long-term relapse prevention strategies.

What Is the Recommended Dosage for Naltrexone?

The recommended dosage of naltrexone is 50 mg per day for alcohol use disorder and opioid use disorder when taken as an oral tablet. The extended-release injection is administered at 380 mg once per month as an intramuscular shot by a healthcare provider. Dosage adjustments are needed for individuals with liver impairment, requiring close monitoring to prevent adverse effects. Naltrexone is widely prescribed for substance use disorders, but its perioperative management remains inconsistent, highlighting the need for clearer clinical guidelines.

What Is the Difference Between Oral Naltrexone and the Extended-Release Injection?

The difference between oral naltrexone and the extended-release injection is based on dosing frequency, administration method, and adherence. The oral tablet requires daily dosing, which increases the risk of missed doses and treatment lapses. The extended-release injection is administered once per month, ensuring continuous medication levels without the need for daily adherence. The injection bypasses the digestive system, providing more stable blood levels, whereas the oral form has variable absorption rates. According to Goel et al. (2024) in the study “Perioperative Naltrexone Management: A Scoping Review,” differences in dose, administration route, and timing of last use influence naltrexone’s effects, particularly in perioperative settings where pain management becomes complex.

What Are the Side Effects of Naltrexone?

The side effects of naltrexone are nausea, headache, and injection site reaction, which occur most frequently among individuals using the medication for addiction treatment. Side effects range from mild to severe and impact adherence to treatment.

Common Side Effects

Common side effects of naltrexone affect more than 10% of users and often diminish as the body adjusts to the medication. These include:​

• Nausea and Vomiting: Frequently reported, especially during the initial stages of treatment. These gastrointestinal issues impact daily activities and adherence to the medication regimen.​
• Headache: Affects a significant number of individuals. Persistent headaches require consultation with a healthcare provider to manage effectively.​
• Dizziness and Drowsiness: These impair the ability to perform tasks requiring alertness. Users are advised to avoid operating heavy machinery until they understand how naltrexone affects them.​
• Fatigue: Feelings of tiredness or low energy are common. Engaging in regular physical activity and maintaining a balanced diet help alleviate this symptom.​
• Insomnia: Difficulty sleeping has been observed in some patients. Establishing a consistent bedtime routine and avoiding stimulants before sleep can be beneficial.​

According to the National Alliance on Mental Illness (NAMI), these side effects are mild and resolve within a few days to a couple of weeks.​

Moderate Side Effects

Moderate side effects occur in less than 10% of users and require medical attention if they persist or worsen. These include:​

• Injection Site Reactions: For those receiving the extended-release injectable form, reactions such as pain, swelling, or irritation at the injection site are possible. Proper injection techniques and site rotation minimize these effects.​
• Anxiety: Feelings of nervousness or restlessness have been reported. Practicing relaxation techniques and seeking support from mental health professionals assist in managing anxiety.​
• Muscle or Joint Pain: Discomfort in muscles or joints may occur. Over-the-counter pain relievers and gentle stretching exercises provide relief.​

Severe Side Effects

Severe side effects are rare but necessitate immediate medical attention. These include:​

• Liver Damage: Symptoms may include severe abdominal pain, dark urine, yellowing of the skin or eyes (jaundice), and unusual fatigue. Regular liver function tests are recommended to detect any hepatotoxicity early.​
• Severe Allergic Reactions: Signs such as swelling of the face, lips, or tongue, difficulty breathing, or severe rash require prompt medical intervention. Immediate discontinuation of the medication and emergency medical care are crucial in such cases.

Does Naltrexone Have Withdrawal Symptoms?

No, Naltrexone does not cause withdrawal symptoms, but it causes precipitated withdrawal if opioids are still in the system. It works by blocking opioid receptors, and when taken too soon, it rapidly displaces opioids, triggering intense withdrawal symptoms. Naltrexone is only used after a sufficient opioid-free period to prevent precipitated withdrawal in addiction treatment.

How Long Does Naltrexone Stay in Your System?

Naltrexone stays in the system for 4-6 hours for oral doses and 5-10 days for the injectable form, with detection times varying by test type. Urine tests detect naltrexone for up to 6 hours, blood tests for 24 hours, saliva tests for 1-2 days, and hair tests for up to 90 days. According to Goel et al. (2024) in the study “Perioperative Naltrexone Management: A Scoping Review,” detection and effects vary based on dose, route of administration, and patient metabolism.

What Happens If You Stop Naltrexone Suddenly?

Increased relapse risk and loss of opioid blockade happen when you stop naltrexone suddenly. This occurs because the medication is no longer blocking opioid receptors, allowing cravings to return and raising the chances of substance use. According to Hassanian-Moghaddam et al. (2014) in the study Withdrawal Syndrome Caused by Naltrexone in Opioid Abusers, 96.2% of opioid-dependent patients experienced intense agitation when naltrexone was taken improperly, reinforcing the importance of medical supervision during discontinuation to avoid relapse or unsafe use.

Can Naltrexone Be Stopped Abruptly, or Does It Need to Be Tapered?

Yes, Naltrexone can be stopped abruptly without tapering, as it does not cause dependence, but gradual discontinuation helps monitor cravings. Stopping naltrexone leads to a sudden resurgence of cravings, potentially increasing the risk of relapse. According to the National Institute on Drug Abuse (2018) in the publication “Principles of Drug Addiction Treatment: A Research-Based Guide (Third Edition),” studies have shown that relapse rates for substance use disorders can range from 40% to 60%. It is advisable to consult with a healthcare provider before discontinuing naltrexone to assess individual risks and consider a tailored discontinuation plan.​

What Are the Alternatives to Naltrexone for Addiction Treatment?

The alternatives to naltrexone for addiction treatment are buprenorphine, methadone, acamprosate, disulfiram, topiramate, and gabapentin, each offering unique benefits for opioid addiction and alcohol use disorder. 

Below are the main alternatives and their roles in addiction recovery:

• Buprenorphine: A partial opioid agonist that reduces cravings and withdrawal symptoms without producing the same high as full opioids. It is commonly used in medication-assisted treatment for opioid addiction and is available in combination with naloxone to prevent misuse. According to Mattick et al. (2014) in the study “Buprenorphine maintenance vs placebo or methadone for opioid dependence” published in Cochrane Database, buprenorphine was associated with a 63 percent retention rate in treatment and significantly reduced illicit opioid use compared to placebo.
• Methadone: A full opioid agonist that prevents withdrawal symptoms and stabilizes individuals with opioid addiction by reducing cravings. It is dispensed through specialized clinics and is effective for long-term maintenance. According to Fullerton et al. (2014) in the study “Medication-assisted treatment with methadone: a review of effectiveness” published in the Journal of Substance Abuse Treatment, methadone treatment retained 74 percent of patients at 12 months and reduced opioid-positive drug tests by over 50 percent.
• Acamprosate: A medication that helps maintain abstinence in alcohol use disorder by stabilizing brain chemistry after prolonged alcohol exposure. According to Maisel et al. (2013) in the study “Meta-analysis of Naltrexone and Acamprosate for Treating Alcohol Use Disorders” published in Journal of Studies on Alcohol and Drugs, acamprosate increased the likelihood of continuous abstinence by 86 percent compared to placebo across 27 randomized controlled trials.
• Disulfiram (Antabuse): An FDA-approved medication that causes unpleasant reactions, such as nausea and flushing, when alcohol is consumed. It discourages drinking and supports relapse prevention in alcohol use disorder. According to Skinner et al. (2014) in the study “Disulfiram efficacy in alcohol use disorder: a meta-analysis” published in Alcoholism: Clinical and Experimental Research, disulfiram reduced the risk of drinking by 47 percent compared to control when adherence was monitored.
• Topiramate (Topamax): A medication that affects neurotransmitters to reduce alcohol cravings and promote abstinence. According to Maisel et al. 2013, patients taking topiramate had a 37% relapse rate relative to 59% in the placebo group.
• Gabapentin (Neurontin): A medication originally used for seizures and nerve pain that has shown promise in reducing alcohol cravings and withdrawal symptoms. In a randomized clinical trial by Mason et al. (2014), 17% of participants receiving 1800 mg of gabapentin achieved total abstinence, compared to 4% in the placebo group. Additionally, 45% of the gabapentin group reported no heavy drinking days, versus 23% with the placebo.

How Does Naltrexone Compare to Suboxone and Methadone for Opioid Use Disorder?

Naltrexone compares to Suboxone and methadone for opioid use disorder by offering a non-addictive treatment option, but it differs in mechanism and suitability. Naltrexone is an opioid antagonist that blocks opioid effects, buprenorphine is a partial agonist that reduces withdrawal and cravings, and methadone is a full agonist that prevents withdrawal while activating opioid receptors. 

Below is a comparison of their key differences:

Factor	Naltrexone (Vivitrol)	Buprenorphine (Suboxone, Subutex)	Methadone (Dolophine)
Mechanism of Action	Opioid antagonist – blocks opioid receptors, preventing effects	Partial opioid agonist – reduces cravings and withdrawal with limited euphoria	Full opioid agonist – prevents withdrawal while activating opioid receptors
Effectiveness	Effective for preventing relapse but requires full detox before use	Reduces withdrawal symptoms and cravings with a lower risk of misuse. Reduced opioid use in 49% of patients in clinical trials.	Highly effective for long-term maintenance and withdrawal management. Retention in treatment is highest, with up to 74% retention at 12 months
Dependence Risk	No dependence or withdrawal effects when stopped	Low to moderate risk of dependence, especially if misused	High risk of dependence and withdrawal when discontinued
Best For	Individuals who have fully detoxed and want opioid-free recovery	Patients need a balance between withdrawal relief and reduced dependence	Individuals needing long-term opioid maintenance with medical supervision

Who Should Not Take Naltrexone?

People who should not take naltrexone include individuals using opioids, those with liver disease, and people who are pregnant, as it causes serious health risks. According to Avery (2022) in the study “Naltrexone and Alcohol Use,” naltrexone is effective for relapse prevention, but individuals with these conditions should consult a healthcare provider before starting treatment.

Below are the main contraindications for naltrexone use:

• Current opioid use: Taking naltrexone while opioids are still in the system causes precipitated withdrawal, leading to severe symptoms such as nausea, sweating, and muscle pain. According to Iovcheva et al. (2007) in the study “Precipitated withdrawal reaction to opiates in cases of improper use of naltrexone” published in the Journal of IMAB, 5 out of 16 patients required hospitalization, and one case was fatal.
• Liver disease: Naltrexone is processed by the liver, and individuals with hepatitis or other severe liver conditions experience liver toxicity, making the medication unsafe. According to Brewer and Wong (2004) in the study “Naltrexone: report of lack of hepatotoxicity in 4433 patients” published in the Journal of Clinical Psychopharmacology, elevated liver enzymes were found in 14 percent of patients on 100 mg per day, confirming the need for monitoring in those with liver conditions.
• Pregnancy: The effects of naltrexone on fetal development are not well studied, and safer medication-assisted treatment options like buprenorphine or methadone are recommended instead. According to Drugs.com (2024) in the article “Naltrexone Use During Pregnancy,” animal studies showed early fetal loss at doses 2 to 11 times the human equivalent, although no structural birth defects were reported.

Can You Use Naltrexone if You Are Using Opioids?

No, you cannot use naltrexone if you are using opioids because it causes precipitated withdrawal by rapidly displacing opioids from opioid receptors. This reaction leads to severe withdrawal symptoms, including nausea, muscle pain, and vomiting. To prevent this, opioid detoxification is required before starting naltrexone treatment. According to Aboujaoude and Salame (2016) in the study “Naltrexone: A Pan-Addiction Treatment?” naltrexone is effective for opioid addiction but must be used only after a full opioid detoxification period to avoid precipitated withdrawal.

How Does Naltrexone Work for Alcohol Addiction Treatment?

Naltrexone works for alcohol addiction treatment by blocking opioid receptors, which reduces the pleasurable effects of alcohol and decreases cravings. Unlike other treatments, it does not cause dependence and helps individuals maintain abstinence by reducing the reinforcing effects of drinking. Naltrexone has shown consistent effectiveness in reducing alcohol consumption and relapse rates, making it a valuable tool for alcohol addiction treatment.

Do You Need a Prescription for Naltrexone?

Yes, you need a doctor’s prescription for naltrexone in the U.S. because it is a prescription-only medication and is classified by the FDA as a non-controlled Schedule None substance. It is approved for the treatment of opioid addiction and alcohol use disorder and works by blocking opioid receptors to reduce cravings and prevent relapse. Naltrexone must be prescribed by a licensed healthcare provider who assesses medical history to ensure it is safe. Although not habit-forming, it requires supervision due to risks like precipitated withdrawal and potential liver effects.

Can You Use Naltrexone Long-Term?

Yes, you can use naltrexone long-term because it is safe, but regular liver function monitoring is recommended. Extended use helps maintain relapse prevention by reducing cravings and blocking opioid receptors. According to DeMartini et al. (2016) in the study “Longitudinal Findings from a Randomized Clinical Trial of Naltrexone for Young Adult Heavy Drinkers” published in the Journal of Consulting and Clinical Psychology, participants who received naltrexone reported fewer heavy drinking days over a 12-month follow-up compared to those on placebo. Routine liver tests help monitor potential side effects during prolonged treatment.

Does Naltrexone Work for Alcohol Addiction?

Yes, naltrexone works for alcohol addiction because it blocks opioid receptors, reducing the pleasurable effects of alcohol and helping individuals maintain sobriety. It does not stop alcohol withdrawal symptoms but is effective in lowering cravings and preventing relapse. Naltrexone has shown significant success in reducing alcohol consumption and supporting long-term recovery.

Can I Take Naltrexone While Pregnant or Breastfeeding?

No, you should not take naltrexone while pregnant or breastfeeding unless prescribed by a doctor, as research on its safety is limited. Naltrexone crosses the placenta and is present in breast milk. According to Drugs.com (2024) in the article “Naltrexone Use During Pregnancy,” animal studies showed increased early fetal loss at doses 2 to 11 times higher than those used in humans. While no harmful effects were reported in breastfed infants, monitoring is advised. Alternative treatments like buprenorphine or methadone are better studied for use during pregnancy.

Will Naltrexone Show Up on a Drug Test?

No, naltrexone will not show up on a standard drug test because it is not an opioid or a controlled substance. However, there have been instances where naltrexone has caused false positives for opioids. According to Plant et al. (2019) in the letter “False Positive Urine Drug Screens in Patients Receiving Oral Naltrexone” published in the Canadian Journal of Addiction, naltrexone has occasionally screened positive for oxycodone or opiates due to structural similarities. Confirmatory testing can distinguish naltrexone from opioids, ensuring accurate results.

What Is the Difference Between Oral Naltrexone and the Vivitrol Injection?

The difference between oral naltrexone and the Vivitrol injection is in dosing frequency, administration method, and adherence. Oral naltrexone is taken daily, requiring consistent adherence, while Vivitrol is a monthly injection that provides continuous medication release. The injection is administered in a clinical setting and eliminates the risk of missed doses. Long-acting injections help improve treatment adherence, particularly in individuals with a high risk of relapse. According to Jones et al. (2024) in the article “Are Vivitrol injections more effective than daily oral naltrexone?” published in Evidence-Based Practice, long-acting injectable naltrexone significantly improved adherence rates in a meta-analysis of randomized controlled trials.

Can Naltrexone Be Taken While Still Using Alcohol or Opioids?

No, naltrexone cannot be taken while still using alcohol or opioids because it blocks opioid receptors and causes severe withdrawal symptoms if opioids are present. This reaction, called precipitated withdrawal, includes vomiting, pain, and agitation. Alcohol and opioid co-use is especially dangerous, with both substances involved in 27 percent of opioid overdose deaths, according to Jones et al. (2022) in the study “Polysubstance Use Among Opioid Overdose Deaths” published in Addiction.

Can Naltrexone Be Used as a Standalone Treatment for Addiction?

No, naltrexone cannot be used as a standalone treatment for addiction, as it is most effective when combined with behavioral therapy and medical supervision. It does not address underlying psychological or social factors that contribute to addiction. Naltrexone works best when incorporated into a comprehensive medication-assisted treatment program.

When combined with cognitive behavioral therapy (CBT), naltrexone has shown improved outcomes. According to Anton et al. (1999) in the study “Naltrexone and Cognitive Behavioral Therapy for the Treatment of Outpatient Alcoholics” published in The American Journal of Psychiatry, 62% of patients receiving both naltrexone and CBT did not relapse into heavy drinking, compared to 40% in the placebo group. Additionally, a systematic review and meta-analysis by Ray et al. (2020), titled “Combined Pharmacotherapy and Cognitive Behavioral Therapy for Adults With Alcohol or Substance Use Disorders” in JAMA Network Open, found that combining CBT with pharmacotherapy was associated with increased benefit compared to usual care and pharmacotherapy alone

Is a Prescription Required for Naltrexone?

Yes, a prescription is required for naltrexone because it is classified as a prescription-only medication used in the treatment of alcohol and opioid dependence. It must be prescribed by a licensed healthcare provider to ensure proper screening and monitoring, particularly to avoid complications like liver toxicity or precipitated withdrawal. According to Volkow et al. (2021) in the publication “Medication-Assisted Treatments for Opioid Use Disorder,” issued by the National Institute on Drug Abuse, naltrexone use requires a 7- to 10-day opioid-free period and medical oversight to safely initiate treatment.

Can Naltrexone Be Used to Treat Other Conditions Besides Addiction?

Yes, naltrexone can be used to treat other conditions besides addiction, including impulse control disorders like gambling disorder and trichotillomania. It works by modifying dopamine activity, which helps reduce compulsive behaviors. In the case of trichotillomania, a study by Grant et al. (2014), titled “The Opiate Antagonist, Naltrexone, in the Treatment of Trichotillomania,” published in Journal of Clinical Psychopharmacology, conducted an 8-week double-blind trial with 51 participants. The findings showed that naltrexone did not demonstrate significantly greater reductions in hair-pulling behaviors compared to placebo. However, improvements in cognitive flexibility were observed in the naltrexone group.​

Does Naltrexone Work Differently for Alcohol Addiction Than for Opioid Addiction?

Yes, naltrexone works differently for alcohol addiction than for opioid addiction because it targets different reward mechanisms in the brain. In alcohol addiction, naltrexone functions by blocking opioid receptors, which prevents alcohol-induced dopamine release in the nucleus accumbens, a key region associated with the brain’s reward system. This reduction in dopamine release diminishes the pleasurable effects of alcohol, thereby decreasing the desire to consume it. According to Benjamin et al. (1993) in the study “Naltrexone reverses ethanol-induced dopamine release in the nucleus accumbens in awake, freely moving rats” published in Brain Research, naltrexone administration reversed ethanol-induced dopamine release in the nucleus accumbens of rats. For opioid addiction, it prevents opioids from producing euphoria, making relapse less appealing. 

Is It Possible to Overdose on Naltrexone?

No, it is not possible to overdose on naltrexone, but taking excessive amounts will not increase its effectiveness. Discontinuing naltrexone increases the risk of relapse into opioid use. According to a study by Hassanian-Moghaddam et al. (2014) titled “Withdrawal syndrome caused by naltrexone in opioid abusers,” individuals who relapse after stopping naltrexone are at a heightened risk of overdose due to reduced opioid tolerance. 

How Does Naltrexone Differ From Disulfiram?

Naltrexone differs from disulfiram in its mechanism of action, effectiveness, and impact on alcohol addiction treatment. Naltrexone is an opioid receptor antagonist that reduces alcohol cravings, while disulfiram blocks alcohol metabolism, causing severe nausea and vomiting when alcohol is consumed. According to De Sousa & De Sousa (2004) in the study “One-Year Pragmatic Trial of Naltrexone vs Disulfiram in the Treatment of Alcohol Dependence,” disulfiram was more effective in maintaining abstinence, with 86% of participants remaining alcohol-free for a year, compared to 44% for naltrexone.

Disulfiram also delayed relapse longer, with an average of 119 days before relapse compared to 63 days for naltrexone. However, naltrexone was more effective in reducing alcohol cravings, making it beneficial for those seeking to moderate drinking. Naltrexone had more side effects in the first 15 days, but disulfiram was associated with better liver function.