Nalmefene: Definition, Mechanism of Action, Uses, Dosage, Side Effects, Alternatives

Nalmefene is used to reduce alcohol consumption in patients with alcohol use disorder (AUD). According to the European Medicines Agency (EMA), nalmefene is approved in Europe for individuals who do not commit to abstinence but need to reduce heavy drinking​.

Nalmefene’s mechanism of action is to block mu (μ) and delta (δ) opioid receptors, preventing alcohol-induced dopamine surges, while its partial kappa (κ) receptor agonism reduces stress-related drinking. A 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” found that patients taking nalmefene had 1.7 fewer heavy drinking days per month compared to placebo​.

Nalmefene is primarily used for reducing alcohol consumption in AUD patients who consume more than 60 g (men) or 40 g (women) of alcohol per day and need a harm-reduction strategy. The UK’s National Institute for Health and Care Excellence (NICE) recommends nalmefene alongside psychosocial support to improve treatment outcomes​.

The recommended dose of nalmefene is 18 mg taken orally as needed, at least 1–2 hours before anticipated drinking, rather than on a fixed daily schedule. A 2014 study by Wim van den Brink et al., “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence,” found that patients who took nalmefene for 12 months maintained reduced alcohol intake without dose escalation​.

Common side effects of nalmefene include nausea (34.2%), dizziness (19.1%), and insomnia (12.5%), which usually subside over time​. Severe side effects, such as suicidal ideation and psychiatric disturbances, led the EMA to issue a warning that nalmefene should not be used in individuals with severe mental health disorders​.

Alternatives for nalmefene include naltrexone, acamprosate, and disulfiram. They are FDA-approved alternatives for AUD treatment, each with distinct mechanisms. A 2015 meta-analysis by Clément Palpacuer et al., “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, found that naltrexone and acamprosate were more effective for long-term alcohol reduction, while disulfiram was best for enforcing abstinence​.

What Is Nalmefene?

Nalmefene is an opioid antagonist used primarily for the treatment of alcohol use disorder (AUD). It is marketed under the brand name Selincro in Europe but has not received FDA approval for alcohol dependence in the United States. However, it has been approved in the U.S. for opioid overdose reversal.

According to a study by Green et al. titled Nalmefene Hydrochloride: Potential Implications for Treating Alcohol and Opioid Use Disorder, published in Substance Abuse and Rehabilitation (2024), nalmefene acts by blocking mu (µ) and delta (δ) opioid receptors while partially activating kappa (κ) receptors. This reduces the reinforcing effects of alcohol, helping to curb cravings and heavy drinking.

Research from the World Health Organization (WHO) also reports that alcohol use disorder (AUD) affects approximately 283 million people globally, including over 14.5 million in the U.S. Despite this, less than 10% of individuals with AUD receive pharmacological treatment. 

Nalmefene significantly reduces heavy drinking days and total alcohol consumption compared to placebo when used in an as-needed approach

What Is the Approval Status of Nalmefene in the U.S.?

The approval status of nalmefene in the U.S. is not FDA-approved for alcohol addiction treatment, meaning it is not available as a prescription medication. While nalmefene is approved in Europe for reducing alcohol consumption, the U.S. Food and Drug Administration (FDA) has not approved it due to concerns over inconsistent clinical trial results and psychiatric side effects. 

A 2015 study by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, reported that nalmefene showed only modest effectiveness in reducing alcohol intake compared to placebo, leading to regulatory hesitations​.

What Is the Mechanism of Action of Nalmefene?

The mechanism of action of nalmefene is based on its ability to regulate opioid receptors in the brain, reducing alcohol’s reinforcing effects. Nalmefene functions as an antagonist at the mu (μ) and delta (δ) opioid receptors while acting as a partial agonist at the kappa (κ) opioid receptor. 

This modulation reduces dopamine release in the mesolimbic system, diminishing the brain’s reward response to alcohol and ultimately reducing cravings. According to a study by MeShell Green et al., titled “Nalmefene Hydrochloride: Potential Implications for Treating Alcohol and Opioid Use Disorder,” published in Substance Abuse and Rehabilitation (2024), nalmefene’s opioid receptor modulation prevents alcohol-induced dopamine surges, making drinking less rewarding​

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When alcohol is consumed, endorphins are released and bind to mu and delta receptors, triggering dopamine release in the nucleus accumbens, a key brain region involved in reward and reinforcement. By blocking mu and delta receptors, nalmefene prevents this dopamine surge, reducing the pleasurable effects of alcohol. 

A randomized controlled trial by Antoni Gual et al. (2013) titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, found that nalmefene significantly reduced alcohol’s rewarding effects by modulating opioid receptor activity​.

Additionally, nalmefene’s partial agonist activity at the kappa receptor plays a role in dampening dopamine release. The kappa-opioid system is associated with stress and dysphoria, and its activation by nalmefene contributes to reducing compulsive alcohol use. 

A study by Wim van den Brink et al., “Long-term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence: A 1-Year Randomized Study,” published in the Journal of Psychopharmacology (2014), confirmed that nalmefene’s action on kappa receptors helps reduce excessive drinking by limiting alcohol-induced euphoria​

What Makes Nalmefene Effective for Reducing Alcohol Cravings?

What makes Nalmefene effective for reducing alcohol cravings is its ability to block mu (μ) and delta (δ) opioid receptors, preventing endorphin-induced dopamine release in the brain’s reward system, making nalmefene effective for reducing alcohol cravings.  This disrupts the reinforcement cycle of alcohol use, making drinking less pleasurable. 

Additionally, its partial agonist activity at the kappa (κ) receptor counteracts dopamine-driven cravings and helps regulate stress-related drinking. According to a 2019 study by Hisatsugu Miyata et al., published in Psychiatry and Clinical Neurosciences, nalmefene 20 mg significantly reduced heavy drinking days by 4.34 days/month by 0.001% compared to placebo, confirming its efficacy in reducing alcohol dependence​.

How Is Nalmefene Used in Alcohol Addiction Treatment?

Nalmefene is used in alcohol addiction treatment as an as-needed medication, meaning it is taken only on days when a person anticipates a strong urge to drink. Unlike daily medication-assisted treatment options like naltrexone, nalmefene provides flexibility in managing alcohol use disorder by blocking opioid receptors and reducing the brain’s dopamine-driven reinforcement of drinking behavior.

Nalmefene is most effective when combined with cognitive behavioral therapy (CBT) or counseling. According to a 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, nalmefene combined with psychosocial support significantly reduced heavy drinking days by 1.7 days/month by 1.2% compared to placebo​.

Additionally, a 2014 study by Wim van den Brink et al., “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence: A 1-Year Randomized Study,” published in the Journal of Psychopharmacology, found that nalmefene plus therapy led to sustained reductions in alcohol consumption over 12 months, reinforcing its effectiveness as part of a comprehensive treatment plan​.

What Are the Clinical Uses of Nalmefene?

The clinical uses of nalmefene include reducing alcohol consumption in alcohol use disorder (AUD) and reversing opioid overdoses. In AUD, nalmefene is prescribed as needed to help individuals cut down on heavy drinking by blocking opioid receptors and reducing alcohol-induced dopamine surges. 

According to a 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, nalmefene reduced heavy drinking days by 1.7 days/month 1.2% compared to placebo when combined with psychosocial support​. 

A 2014 study by Wim van den Brink et al., “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence: A 1-Year Randomized Study,” published in the Journal of Psychopharmacology, confirmed that nalmefene maintained reductions in alcohol consumption for up to 12 months​.

Nalmefene is also used in opioid overdose reversal. It is structurally related to naloxone but has a longer half-life, making it effective for reversing overdoses from long-acting opioids like fentanyl. 

A 2024 study by MeShell Green et al., titled “Nalmefene Hydrochloride: Potential Implications for Treating Alcohol and Opioid Use Disorder,” published in Substance Abuse and Rehabilitation, highlighted that nalmefene has a 5-fold higher binding affinity to opioid receptors than naloxone, making it more effective against synthetic opioids​.

Is Nalmefene Used Off-Label for Other Conditions?

Yes, nalmefene is used off-label for other conditions such as pathological gambling, impulse control disorders, and pruritus associated with liver disease. A 2006 study by Jon E. Grant et al., titled “Multicenter Investigation of the Opioid Antagonist Nalmefene in the Treatment of Pathological Gambling,” published in The American Journal of Psychiatry, found that nalmefene significantly reduced pathological gambling symptoms by 0.02% compared to placebo​

 The off-label uses of nalmefene for other conditions include:

• Pathological Gambling: Nalmefene has been investigated as a treatment for gambling addiction due to its ability to modulate the opioid system and reduce compulsive behaviors. It works by blocking the mu-opioid receptors, which are involved in the brain’s reward system, thus decreasing the reinforcing effects of gambling. A 2006 study by Jon E. Grant et al. titled “Multicenter Investigation of the Opioid Antagonist Nalmefene in the Treatment of Pathological Gambling,” published in The American Journal of Psychiatry, found that nalmefene significantly reduced gambling severity scores compared to placebo​.
• Impulse Control Disorders: Nalmefene is being explored for impulse control disorders, including compulsive shopping, internet addiction, and kleptomania, due to its effects on dopaminergic reinforcement mechanisms. Modulating opioid receptor activity reduces reward-seeking behavior, which is common in these disorders. A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, identified studies where nalmefene showed potential benefits in reducing impulsive behaviors but noted higher dropout rates due to side effects.
• Pruritus Associated with Liver Disease: Nalmefene has been investigated for chronic pruritus in liver diseases such as cholestasis, where opioid system dysregulation is implicated in itching. By blocking excessive opioid receptor activation in the central nervous system, nalmefene reduces severe itching and is unresponsive to conventional treatments. A 2004 study by Nora V. Bergasa et al., titled “Open-Label Trial of Oral Nalmefene Therapy for the Pruritus of Cholestasis,” published in Hepatology, found that 13 out of 14 patients reported itch relief, with significant reductions in scratching behavior 0.2%​.

What Is the Recommended Dosage of Nalmefene?

The recommended dosage of nalmefene is 18 mg taken orally as needed, preferably 1–2 hours before a person anticipates drinking alcohol. Unlike other treatments for alcohol use disorder, which require daily administration, nalmefene follows an as-needed regimen, allowing individuals to control cravings based on their drinking patterns.

The standard dose requires adjustments based on individual factors, including liver function, kidney function, and concurrent medications. Patients with moderate to severe hepatic or renal impairment experience altered nalmefene metabolism, leading to prolonged drug effects and potential side effects. 

Additionally, individuals on opioid-based pain medications should not take nalmefene, as it could trigger opioid withdrawal symptoms. A 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, confirmed that 18 mg of nalmefene reduced alcohol consumption significantly when paired with psychosocial support​.

How Is Nalmefene Taken for Best Results?

Nalmefene is taken orally as an 18 mg tablet, preferably 1–2 hours before anticipated alcohol consumption, and should be combined with counseling or cognitive behavioral therapy (CBT) for best results. 

A 2014 study by Wim van den Brink et al., titled “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence: A 1-Year Randomized Study,” published in the Journal of Psychopharmacology, found that Nalmefene, when paired with psychosocial support, led to sustained reductions in alcohol intake over 12 months​.

Tips for taking nalmefene for best results include:

• Timing: Nalmefene should be taken 1–2 hours before alcohol consumption, as this allows the medication to reach peak plasma concentration and effectively block opioid receptors before drinking occurs. It is not effective if taken after drinking has already started, as it does not reverse the effects of alcohol but instead reduces the motivation to drink. A 2014 study by Wim van den Brink et al., titled “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence,” published in the Journal of Psychopharmacology, confirmed that consistent pre-drinking use led to greater reductions in alcohol consumption over time​.
• Dietary Considerations: Nalmefene is taken with or without food, as its absorption is not significantly affected by meals. However, individuals should avoid consuming excessive fatty meals, as high-fat content slightly delays drug absorption but does not reduce its effectiveness. Patients should also avoid grapefruit juice, as it interferes with liver enzymes that metabolize nalmefene, potentially altering its effects​.
• Adherence Tips: To maximize effectiveness, individuals should set reminders to take nalmefene on high-risk drinking days and track their drinking patterns to anticipate cravings. Healthcare providers often recommend keeping nalmefene readily available, such as carrying it in a bag or storing it in a visible location at home, to ensure timely use. Engaging in behavioral therapy, such as cognitive behavioral therapy (CBT), enhances adherence by reinforcing coping strategies and helping individuals recognize triggers for alcohol consumption​.

What to Do If You Missed a Dose of Nalmefene?

Do not take nalmefene if you miss a dose of nalmefene and it is close to the next anticipated drinking episode, as doubling up on doses increases the risk of side effects. If you miss a dose but still plan to drink alcohol later in the day, take one 18 mg tablet as soon as you remember, at least 1–2 hours before drinking. 

However, if you have already gone without alcohol for the day, simply skip the missed dose and take nalmefene as needed on the next occasion. A 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, emphasized that nalmefene should be taken only when necessary and not on a strict daily schedule​.

What Are the Side Effects of Nalmefene?

The side effects of nalmefene include common, rare, and serious adverse effects, which vary in severity and duration. Common side effects include nausea, dizziness, insomnia, and headaches, occurring within the first few doses as the body adjusts to the medication. 

Rare side effects include fatigue, excessive sweating, and blurred vision, which usually resolve over time but require medical attention if they are persistent. Serious side effects, though uncommon, include severe mood changes, confusion, hallucinations, or withdrawal symptoms in opioid-dependent individuals, requiring immediate medical intervention. 

A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, found that patients taking nalmefene had a significantly higher dropout rate due to adverse effects compared to placebo​.

What Are the Most Common Side Effects of Nalmefene?

The most common side effects of nalmefene are nausea, dizziness, insomnia, headaches, and fatigue. These effects interfere with the individual’s day-to-day activities, especially as the body adjusts to the medications. 

The most common side effects of nalmefene include:

• Nausea: A frequent side effect, nausea is usually mild to moderate and tends to occur within the first few doses as the body adjusts to the medication. Most cases resolve within a few weeks without intervention, though severe nausea requires dose adjustments. A 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, reported that nausea affected 34.2% of nalmefene users compared to 5.6% in the placebo group
• Dizziness: This occurs due to opioid receptor modulation affecting the central nervous system, leading to a sensation of imbalance or lightheadedness. While mild and transient, dizziness interferes with daily activities, especially during the first week of treatment. A 2014 study by Wim van den Brink et al., titled “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence: A 1-Year Randomized Study,” published in the Journal of Psychopharmacology, found that dizziness was reported in 19.1% of nalmefene users compared to 6.2% of placebo users​.
• Insomnia: Sleep disturbances, including difficulty falling asleep or frequent awakenings, are commonly reported during the initial weeks of treatment. These symptoms generally improve over time, but persistent cases require adjusting the time of nalmefene intake. A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, noted that insomnia occurred in 12.5% of patients taking nalmefene compared to 4.8% in the placebo group.
• Headaches: Mild to moderate headaches are common and linked to neurotransmitter modulation caused by nalmefene. These headaches subside within the first few weeks and are managed with hydration and over-the-counter pain relievers​.
• Fatigue: Some patients report feeling unusually tired or low in energy, particularly in the first few days of treatment. This side effect is habitually temporary and improves as the body adapts to the medication. The 2014 study by van den Brink et al. found that fatigue was reported in 9.8% of nalmefene users versus 4.1% in the placebo group​

Are There Any Serious or Long-Term Side Effects of Nalmefene?

Yes, psychiatric disturbances, withdrawal symptoms in opioid-dependent individuals, and hepatotoxicity are the serious or long-term side effects of nalmefene. Some patients experience severe mood changes, depression, anxiety, or suicidal ideation, particularly in the early weeks of treatment, likely due to opioid receptor modulation affecting neurotransmitter balance. 

The European Medicines Agency (EMA) issued a warning stating that nalmefene should be used with caution in individuals with a history of mental health disorders due to an increased risk of suicidal thoughts and behaviors​.

Additionally, nalmefene triggers opioid withdrawal symptoms in individuals with recent opioid use, leading to nausea, vomiting, sweating, and agitation. This is because nalmefene displaces opioids from mu receptors, causing an abrupt withdrawal reaction. 

A 2024 study by MeShell Green et al., titled “Nalmefene Hydrochloride: Potential Implications for Treating Alcohol and Opioid Use Disorder,” published in Substance Abuse and Rehabilitation, found that patients with a history of opioid use experienced severe withdrawal symptoms when given nalmefene​.

Long-term use of nalmefene also carries a risk of liver toxicity, particularly in patients with pre-existing liver disease. Since the drug is metabolized in the liver, prolonged use leads to elevated liver enzyme levels and potential hepatotoxic effects. 

A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, reported that patients on nalmefene had a higher incidence of liver enzyme abnormalities compared to placebo.

How to Manage Nalmefene’s Side Effects?

To manage nalmefene’s side effects, patients should start with the lowest effective dose, take the medication with food to reduce nausea, and stay hydrated to minimize headaches and dizziness. 

A 2014 study by Wim van den Brink et al., titled “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence: A 1-Year Randomized Study,” published in the Journal of Psychopharmacology, found that side effects were less severe by 0.5% when nalmefene was introduced gradually and combined with psychosocial support ​.

Ways to manage  nalmefene’s side effects include:

• Take with Food: Nalmefene causes nausea and dizziness, which is reduced by taking the medication with a meal or snack. Food slows the absorption rate, preventing sudden peaks in drug levels that trigger discomfort. A 2014 study by Wim van den Brink et al., titled “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence,” published in the Journal of Psychopharmacology, found that patients who took nalmefene with food reported fewer gastrointestinal side effects.
• Stay Hydrated: Drinking plenty of water throughout the day helps counteract headaches, dizziness, and dry mouth, which are common early side effects. Dehydration worsens these symptoms, so patients should aim for at least 8–10 glasses of water daily. A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, reported that patients with adequate hydration had significantly lower rates of dizziness and fatigue​.
• Avoid Alcohol and Opioids: Nalmefene causes severe withdrawal symptoms if taken by individuals who have recently used opioids, and consuming alcohol while on nalmefene increases nausea, confusion, and dizziness. Patients should inform their doctor about any opioid-based medications before starting treatment to avoid adverse effects. A 2024 study by MeShell Green et al., titled “Nalmefene Hydrochloride: Potential Implications for Treating Alcohol and Opioid Use Disorder,” published in Substance Abuse and Rehabilitation, highlighted that patients with prior opioid use experienced severe withdrawal reactions when given nalmefene.
• Monitor Mood Changes: Some individuals experience anxiety, mood swings, or depressive symptoms, especially in the first few weeks of treatment. Patients should track mood changes and consult a doctor if they experience suicidal thoughts, persistent depression, or agitation. The European Medicines Agency (EMA) has warned that nalmefene increases the risk of psychiatric side effects in patients with a history of mental health conditions​.
• Seek Medical Help for Severe Reactions: If a patient experiences severe allergic reactions, hallucinations, confusion, or extreme dizziness, they should immediately stop nalmefene and seek emergency medical care. These symptoms indicate a serious adverse reaction requiring urgent medical intervention. A 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, noted that patients experiencing severe psychiatric or neurological symptoms were advised to discontinue nalmefene under medical supervision​

What Are the Alternative Medications to Nalmefene for Alcohol Addiction?

The alternative medications to nalmefene for alcohol addiction are naltrexone, acamprosate, and disulfiram, each working through different mechanisms to reduce alcohol consumption. A 2015 study by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, found that naltrexone and acamprosate were more effective for long-term alcohol reduction, while disulfiram was best for enforcing abstinence.

The alternative medications to nalmefene for alcohol addiction are explained below:

• Naltrexone: A mu-opioid receptor antagonist, naltrexone blocks the pleasurable effects of alcohol by preventing alcohol-induced dopamine surges in the brain’s reward system. It is available in oral (50 mg daily) and extended-release injectable (380 mg monthly) forms, making it a flexible treatment option. A 2015 study by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, found that naltrexone significantly reduced heavy drinking days by 1% compared to placebo.
• Acamprosate: Unlike opioid antagonists, acamprosate works on glutamate and GABA neurotransmission, helping to restore brain chemistry disrupted by chronic alcohol use. It is particularly effective in reducing withdrawal symptoms and preventing relapse, making it ideal for those aiming for long-term abstinence. The 2015 study by Palpacuer et al. also found that acamprosate improved abstinence rates in alcohol-dependent individuals over six months​.
• Disulfiram: This medication inhibits aldehyde dehydrogenase, an enzyme involved in alcohol metabolism, causing severe nausea, vomiting, and flushing if alcohol is consumed. It does not reduce cravings but acts as a deterrent for individuals who are highly motivated to quit drinking. A 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, noted that disulfiram was effective in promoting abstinence but required strong patient commitment due to its aversive reaction to alcohol​.

How Does Nalmefene Differ from Naltrexone in Treating Alcohol Dependence?

Nalmefene differs from naltrexone in treating alcohol dependence through its as-needed dosing regimen, whereas naltrexone is taken daily. Both drugs work as opioid receptor antagonists, but nalmefene is a partial kappa receptor agonist, which further reduces alcohol cravings by modulating stress-related drinking. 

Naltrexone has stronger evidence from FDA-approved studies, showing higher effectiveness in reducing heavy drinking days and relapse rates, while nalmefene is primarily used in Europe for harm reduction. 

A 2015 meta-analysis by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, found that naltrexone had greater efficacy of 1% in reducing alcohol consumption compared to nalmefene.

The table below shows how nalmefene differs from naltrexone in treating alcohol dependence:

How Effective Is Nalmefene for Alcohol Addiction Treatment?

Nalmefene for alcohol addiction treatment is very effective in reducing heavy drinking but less effective for complete abstinence. It works best for patients who are unable or unwilling to quit drinking completely and aims to reduce overall alcohol intake rather than enforce sobriety. 

A 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, found that nalmefene reduced heavy drinking days by 1.7 days/month by 1.2% compared to placebo, with greater benefits in individuals who did not attempt to reduce drinking before treatment​.

Nalmefene significantly lowers alcohol consumption and the number of heavy drinking days, particularly in individuals with high baseline alcohol intake. However, its effectiveness depends on treatment adherence, motivation, and concurrent psychosocial support, as it is not a standalone solution. 

A 2014 long-term study by Wim van den Brink et al., “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence,” published in the Journal of Psychopharmacology, found that patients who continued nalmefene treatment for 12 months maintained significant reductions in alcohol consumption compared to those who discontinued use.

Is Nalmefene Available Over the Counter in the U.S.?

No, nalmefene is not available over the counter in the U.S. and is classified as a prescription drug. While it is approved in Europe for reducing alcohol consumption, the U.S. Food and Drug Administration (FDA) has not authorized its use for alcohol dependence. 

According to a 2015 study by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, nalmefene has not met the FDA’s approval criteria due to concerns over its efficacy and psychiatric side effects​.

What Are the Contraindications for Nalmefene?

The contraindications for nalmefene include current opioid use, severe liver or kidney impairment, and a history of severe psychiatric disorders. A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, found that nalmefene triggered severe withdrawal symptoms in opioid-dependent patients and increased psychiatric side effects in individuals with a history of depression or anxiety​

The contradictions for nalmefene are explained below:

• Current Opioid Use: Nalmefene is a mu-opioid receptor antagonist, meaning it induces immediate withdrawal symptoms in individuals using opioid medications or illicit opioids. Symptoms include severe nausea, vomiting, sweating, agitation, and tremors, requiring emergency medical intervention. A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, found that opioid-dependent patients experienced a 1% severe withdrawal reaction when given nalmefene​.
• Severe Liver or Kidney Impairment: Since nalmefene is metabolized in the liver and excreted by the kidneys, individuals with severe hepatic or renal dysfunction experience delayed drug clearance, increasing the risk of toxicity and adverse effects. Liver enzyme levels should be monitored regularly in patients with moderate hepatic impairment who are prescribed nalmefene. A 2015 study by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, reported that patients with pre-existing liver conditions showed higher 0.5% rates of hepatotoxicity with nalmefene use​.
• History of Severe Psychiatric Disorders: Nalmefene has been associated with mood disturbances, depression, anxiety, and suicidal ideation, particularly in individuals with a history of psychiatric illness. It worsens underlying mental health conditions, leading to increased psychological distress or psychiatric emergencies. The European Medicines Agency (EMA) has issued a safety warning regarding psychiatric risks associated with nalmefene use, especially in patients with pre-existing mental health disorders​

Does Nalmefene Interact with Alcohol?

Nalmefene interacts with alcohol by blocking its rewarding effects but does not cause adverse reactions when consumed together. Unlike disulfiram, which induces severe illness when alcohol is ingested, nalmefene allows drinking but reduces cravings and the pleasurable reinforcement of alcohol consumption. 

However, continuing to drink alcohol while on nalmefene reduces the effectiveness of treatment, as the medication is designed to help individuals gradually decrease alcohol intake. A 2013 study by Antoni Gual et al., titled “A Randomized, Double-Blind, Placebo-Controlled Study of Nalmefene in Alcohol Dependence,” published in European Neuropsychopharmacology, confirmed that patients who reduced alcohol intake while using nalmefene had better long-term outcomes of 1.2% compared to those who continued heavy drinking​.

Are There Any Drug Interactions With Nalmefene?

Yes, there are drug interactions with nalmefene. Nalmefene interacts with opioid medications, central nervous system depressants, and certain psychiatric drugs, which reduces effectiveness or increases the risk of side effects. 

A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, found that patients taking opioid-based pain relievers or sedatives experienced heightened withdrawal symptoms and central nervous system depression when combined with nalmefene​.

The drugs that interact with nalmefene include:

• Opioid Medications (e.g., Morphine, Oxycodone, Fentanyl): Nalmefene blocks opioid receptors, meaning it triggers sudden and severe withdrawal symptoms in individuals taking opioid pain relievers or undergoing opioid replacement therapy. Symptoms include nausea, vomiting, sweating, tremors, and agitation, requiring immediate medical intervention. A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, found that opioid-dependent patients who took nalmefene experienced significant withdrawal reactions​.
• Central Nervous System (CNS) Depressants (e.g., Benzodiazepines, Barbiturates, Alcohol): Combining nalmefene with CNS depressants increases drowsiness, dizziness, and cognitive impairment, affecting reaction time and coordination. This interaction is particularly dangerous for individuals who operate heavy machinery or drive, as it increases the risk of accidents. A 2015 study by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, found that patients using nalmefene alongside sedative medications had higher rates of dizziness and confusion, up to 0.5%​.
• Antidepressants and Antipsychotics (e.g., SSRIs, SNRIs, Atypical Antipsychotics): Nalmefene interacts with psychiatric medications by altering neurotransmitter balance, potentially worsening mood symptoms or reducing medication efficacy. Patients with a history of depression or anxiety should be closely monitored, as nalmefene has been linked to increased psychiatric side effects, including suicidal thoughts in vulnerable individuals. The European Medicines Agency (EMA) has issued a warning regarding psychiatric risks associated with nalmefene, particularly in individuals taking concurrent psychotropic medications​

Who Should Not Take Nalmefene?

Opioid users, individuals with severe liver or kidney disease, and those with a history of severe psychiatric disorders should not take nalmefene. These individuals are at a higher risk of severe withdrawal symptoms, toxicity, or worsening mental health conditions, making nalmefene unsafe for use in these cases.

People who should not take nalmefene are as follows:

• Opioid Users (Patients on Opioid Medications or Opioid Use Disorder Treatment): Nalmefene blocks opioid receptors, leading to sudden and severe withdrawal symptoms in individuals currently using opioid pain relievers or opioid substitution therapy. Symptoms such as nausea, vomiting, tremors, and agitation are dangerous and require emergency medical intervention. A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, found that patients on opioid therapy who took nalmefene experienced significant 0.1% withdrawal reactions​.
• Patients with Severe Liver or Kidney Disease: Nalmefene is metabolized in the liver and excreted by the kidneys, meaning individuals with hepatic or renal impairment experience prolonged drug effects and toxicity. High levels of nalmefene in the bloodstream increase the risk of side effects, including confusion, dizziness, and nausea. A 2015 study by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, reported that patients with liver disease had a 0.5% higher risk of hepatotoxicity when using nalmefene.
• Individuals with Severe Psychiatric Disorders (Depression, Anxiety, Schizophrenia, or Suicidal Tendencies): Nalmefene has been linked to mood disturbances, increased anxiety, and suicidal ideation, particularly in those with pre-existing psychiatric conditions. The drug’s effect on neurotransmitter balance exacerbates symptoms or interferes with psychiatric medications, increasing psychological distress. The European Medicines Agency (EMA) issued a warning stating that nalmefene increases the risk of psychiatric side effects, especially in individuals with a history of depression or schizophrenia​

Can Nalmefene Be Used During Pregnancy or Breastfeeding?

No, nalmefene is not recommended during pregnancy or breastfeeding due to insufficient human clinical data on fetal safety. Animal studies have shown potential risks to fetal development, but the FDA has not assigned nalmefene a specific pregnancy category due to limited research. 

Additionally, since nalmefene is excreted in breast milk, it affects neonatal opioid receptors, posing unknown risks to infants. A 2015 study by Clément Palpacuer et al., titled “Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence,” published in PLOS Medicine, emphasized the lack of human safety data and the need for caution when prescribing nalmefene to pregnant or lactating women​.

Can Nalmefene Cause Dependence?

No, nalmefene does not cause physical dependence because it is an opioid antagonist, meaning it does not activate opioid receptors or produce euphoric effects. However, some individuals develop a psychological reliance on the medication, believing they cannot control their drinking without it. 

A 2017 systematic review by Karina G. Vincents Johansen et al., titled “Harms Associated with Taking Nalmefene for Substance Use and Impulse Control Disorders,” published in PLOS ONE, confirmed that nalmefene has no known abuse potential or withdrawal symptoms.

How Safe Is the Long-Term Use of Nalmefene?

The long-term use of nalmefene is safe, with sustained efficacy in reducing alcohol consumption without significant tolerance development. However, regular monitoring for side effects, particularly psychiatric symptoms, liver function, and adherence issues, is recommended. 

A 2014 study by Wim van den Brink et al., titled “Long-Term Efficacy, Tolerability, and Safety of Nalmefene in Alcohol Dependence: A 1-Year Randomized Study,” published in the Journal of Psychopharmacology, found that patients using nalmefene for 12 months maintained reduced alcohol intake without developing increased side effects or needing higher doses.