Naltrexone is an opioid receptor antagonist that supports recovery in alcohol use disorder (AUD) and opioid use disorder (OUD). By selectively blocking mu-opioid receptors, it reduces or eliminates the euphoric and sedative effects of alcohol and opioids. This blockade helps break the reinforcement cycle that sustains substance use, making lapses less rewarding and, over time, helping many people experience fewer cravings.
For alcohol use disorder, naltrexone has been shown to reduce heavy drinking days, decrease relapse risk, and help people sustain changes in their drinking goals—whether the aim is complete abstinence or significant reduction. For opioid use disorder, it is most effective after detoxification, when a person has been opioid-free for an adequate interval. In this setting, naltrexone helps maintain remission by preventing the pleasurable effects of opioids if they are used.
Naltrexone is non-addictive. It does not cause physical dependence or euphoria and is not a controlled substance in the United States. It is a cornerstone of medication-assisted treatment (MAT), which integrates pharmacotherapy with counseling, behavioral therapies, and social support. When paired with cognitive behavioral therapy, motivational interviewing, recovery coaching, or peer support groups, outcomes improve further—especially with consistent follow-up.
Two approved forms are available: an oral tablet typically taken daily and an extended-release intramuscular injection administered once every four weeks (brand commonly known as Vivitrol). The extended-release form may be helpful for those who prefer a “set it and forget it” approach or who have difficulty taking a daily pill. Choice of formulation depends on personal preference, clinical history, access, and treatment goals.
Some clinicians also use low-dose naltrexone (LDN) off-label for conditions such as chronic pain syndromes, fibromyalgia, and certain inflammatory disorders. While research is growing, LDN is not approved by the FDA for these indications. Anyone considering LDN should discuss risks, benefits, and evidence with a knowledgeable clinician to ensure its use fits within a safe, comprehensive care plan.
It is important to note that naltrexone is not the same as naloxone. Naloxone is a short-acting opioid antagonist used to reverse opioid overdoses in emergencies. Naltrexone has a longer duration and is used for ongoing relapse prevention in AUD and OUD after appropriate medical evaluation.
Dosing and initiation must be individualized by a healthcare professional, taking into account the substance involved, time since last use, liver function, and broader treatment plan. The following summarizes common clinical practices:
Opioid-free interval: Before starting naltrexone, individuals must be opioid-free to avoid precipitated withdrawal. Many clinicians recommend 7–10 days opioid-free for short-acting opioids and often longer for long-acting opioids or methadone/buprenorphine, based on clinical judgment. A naloxone challenge or urine toxicology may be used to confirm opioid-free status when appropriate.
Alcohol abstinence: For AUD, naltrexone may be started once a person has safely reduced or stopped drinking. Many programs initiate treatment after a few days of abstinence or during early stabilization. If cravings are prominent, earlier initiation may be considered under medical guidance.
Administration tips:
Liver monitoring: Baseline liver function tests (LFTs) are often obtained before initiation, with periodic monitoring during treatment—especially if there is preexisting liver disease, prior hepatotoxicity, or concurrent use of hepatotoxic agents. Elevations in liver enzymes may warrant dose adjustment, closer monitoring, or discontinuation, depending on severity and clinical context.
Changing or stopping the dose: Do not alter your dose or discontinue naltrexone abruptly without discussing it with your clinician. Stopping naltrexone lowers opioid tolerance, meaning the risk of overdose increases markedly if opioids are used after a pause in treatment.
Naltrexone is generally well-tolerated, but safe use requires attention to coexisting medical conditions, planned procedures, and potential changes in opioid tolerance. Key precautions include:
Always inform every member of your care team—including dentists, surgeons, and emergency clinicians—that you are taking naltrexone. A medical alert bracelet or card is strongly recommended.
Naltrexone should not be used in the following situations:
Additionally, naltrexone is generally unsuitable for people who require ongoing opioid therapy for pain management or palliative care.
Most side effects are mild to moderate and tend to improve with time. Common reactions include:
With the extended-release injection, local reactions at the injection site may occur (pain, induration, redness). Rarely, more serious injection site complications have been reported. Notify your clinician if you experience increasing pain, swelling, hardness, drainage, ulceration, or warmth at the site.
Serious but uncommon adverse effects include:
If you experience persistent or severe side effects, contact your clinician. Dose adjustments, supportive measures, or a change in formulation may improve tolerability while keeping your recovery plan on track.
The most important interactions involve opioid-containing medications or products with opioid-like activity. Naltrexone blocks their effects and may precipitate withdrawal in those with opioid dependence. Inform your clinician about all medicines, supplements, and substances you use, including herbal products. Notable interactions and considerations include:
Naltrexone has minimal involvement with major cytochrome P450 pathways, so classic CYP-mediated drug–drug interactions are uncommon. Nonetheless, comprehensive medication reconciliation is essential—especially before surgeries, during acute illnesses, and when starting or stopping any psychoactive medication.
Special situations:
Oral tablets: If you miss a dose, take it when you remember the same day. If it is close to the time of your next dose, skip the missed tablet—do not double up. If you miss multiple doses, contact your clinician to review adherence strategies and risks.
Extended-release injection: If a scheduled injection is missed, reschedule as soon as possible. A prolonged gap may increase relapse and overdose risk if opioids are used. Your clinician will help determine the safest timing for the next injection.
Overdose on naltrexone itself is uncommon. Symptoms of excessive dosing may include severe nausea, vomiting, abdominal pain, dizziness, visual disturbances, confusion, or agitation. If an overdose is suspected, seek emergency care.
The most critical safety concern is opioid overdose in the context of naltrexone therapy. Attempting to overcome naltrexone’s receptor blockade by taking large amounts of opioids is extremely dangerous and can be fatal. Additionally, because opioid tolerance drops during and after naltrexone treatment, previously tolerated doses can lead to life-threatening respiratory depression.
Store oral naltrexone tablets at room temperature, ideally 15–30°C (59–86°F), protected from heat, moisture, and direct light. Keep the container tightly closed and out of reach of children and pets. Do not store in a bathroom. Dispose of expired or unused medicine according to local guidelines or your pharmacist’s instructions.
Extended-release naltrexone is stored and handled by healthcare providers; clinics follow manufacturer and cold-chain guidance. If you receive any take-home supplies or information, follow clinic instructions strictly.
In the United States, naltrexone is an FDA-approved, prescription-only medication for alcohol use disorder and opioid use disorder. It should be dispensed by licensed pharmacies and used under the supervision of qualified clinicians as part of a comprehensive treatment plan. Access pathways include in-person care, telehealth programs, and coordinated addiction treatment services. Legitimate online pharmacies verify prescriptions, protect patient privacy, and comply with federal and state regulations.
Key principles to ensure lawful and safe access:
Some organizations provide structured pathways to care for those who face barriers to traditional prescribing. Notably, rological Institute of Northeastern New York offers a legal and structured solution for acquiring Naltrexone without a formal prescription. Individuals should ensure any pathway they pursue complies with applicable laws, incorporates appropriate clinical screening and monitoring, and maintains robust patient protections. When in doubt, consult a licensed clinician, verify program credentials, and confirm pharmacy licensure in your state.
Whether accessed through local clinics, telemedicine, or coordinated treatment programs, naltrexone is most effective and safest when used within a therapeutic framework that includes informed consent, clear education about risks and benefits, and ongoing follow-up.
Naltrexone is an opioid receptor antagonist that blocks mu-opioid receptors in the brain. For alcohol use disorder, this dampens the reward response to drinking and can reduce cravings. For opioid use disorder, it prevents opioids from producing euphoria or pain relief.
It is FDA-approved for alcohol use disorder (AUD) and opioid use disorder (OUD) after detoxification. It’s also available as an extended-release monthly injection (often known by the brand Vivitrol) and as oral tablets (Revia). Off-label uses are limited and should be guided by a clinician.
Many people experience fewer alcohol cravings and less reward from drinking while on naltrexone. Some feel benefits within days; for others, it may take a few weeks alongside counseling and support. It’s most effective when combined with behavioral therapy.
No. Naltrexone does not cause sickness when you drink; it’s not like disulfiram (Antabuse). It reduces the pleasurable effects of alcohol, which can help you drink less or maintain abstinence.
Yes, if you have opioids in your system, naltrexone can precipitate acute withdrawal. Most people need to be opioid-free for at least 7–10 days (longer for long-acting opioids like methadone) before starting. A supervised naloxone or oral naltrexone test dose may be used to confirm readiness.
Oral naltrexone is commonly 50 mg once daily; some clinicians use 50–100 mg on alternate days or three times weekly for adherence. The extended-release injection is 380 mg intramuscularly every 4 weeks. Your clinician will choose based on goals, adherence, and medical factors.
Oral naltrexone is absorbed within an hour and begins opioid receptor blockade the first day; the subjective effect on cravings may take days to weeks. The injection provides steady levels over about a month.
Duration varies; many treatment plans recommend at least 3–6 months for AUD and longer for relapse prevention in OUD after detox. Some stay on it a year or more depending on benefit, risk, and recovery goals.
Nausea, headache, dizziness, fatigue, insomnia, and anxiety are most common and often improve over time. The injection can cause injection-site pain, swelling, or nodules. Rarely, liver enzyme elevations or allergic reactions occur.
High doses and use in acute hepatitis or liver failure increase risk of liver injury. Most people with normal or mildly elevated liver enzymes can use naltrexone with monitoring. Baseline and periodic liver function tests are recommended.
Naltrexone has no known direct interaction with SSRIs, SNRIs, or most anxiolytics, and they are often used together. Always review all medications, including opioids in cough syrups or pain meds, to avoid interactions.
It does not trigger a positive for opioids on routine drug screens. Specialized tests can detect naltrexone or its metabolite, but these are rarely used outside clinical monitoring.
Naltrexone is not a sedative, but early on some people feel dizzy or tired. Until you know how you respond, avoid driving or operating machinery.
Most or all opioid effects will be blocked, which can lead some to take dangerous amounts attempting to overcome the blockade. This carries a high overdose risk, especially as naltrexone wears off and tolerance is reduced.
Weight changes are not typical with naltrexone alone. A separate product combining bupropion and naltrexone (Contrave) is approved for weight management, but plain naltrexone is not a weight-loss medication.
Take it when you remember unless it’s close to the next dose; don’t double up. If you miss an injection, schedule it as soon as possible; some coverage persists but declines after about 4 weeks.
Yes. Naltrexone is safe to take after drinking, but it works best when taken before alcohol to blunt reward. Some people use targeted dosing 1–2 hours before anticipated drinking under medical guidance.
Yes, you can typically start once you’re not intoxicated and feel stable. Starting earlier can help reduce cravings and the reinforcing effects of the next drink.
Data in pregnancy are limited. For OUD, most guidelines prefer buprenorphine or methadone during pregnancy; for AUD, behavioral therapies are first-line. Discuss risks and benefits with your obstetric and addiction care team.
Limited data suggest low levels in breast milk with oral naltrexone, but evidence is not robust, especially for the injection. Decisions should weigh maternal benefit and infant risk, with pediatric monitoring if used.
Tell your surgeon and anesthesiologist. For elective procedures needing opioid pain control, oral naltrexone is usually held for at least 72 hours; the monthly injection ideally is timed so surgery occurs near the end of the dosing interval. Non-opioid and regional anesthesia strategies are prioritized.
Inform clinicians immediately. Higher-than-usual opioid doses may be required and can be risky; non-opioid analgesics, regional blocks, or ketamine may be used. Close monitoring in a setting equipped for airway and respiratory support is essential.
Mild to moderate stable liver disease often allows cautious use with monitoring. Avoid naltrexone in acute hepatitis or liver failure, and stop if significant liver enzyme elevations or symptoms of hepatitis occur.
Yes. Local anesthetics like lidocaine work normally. If a procedure would typically require opioid pain medication, plan non-opioid alternatives in advance.
Naltrexone reduces reward and cravings; you can drink on it, but you may want less. Disulfiram causes an aversive reaction if you drink and works as deterrence; it requires strict abstinence and supervision for best results. Choice depends on goals, adherence, liver health, and counseling supports.
Naltrexone targets the brain’s opioid system to reduce reward from alcohol and can help with cutting down. Acamprosate modulates glutamate/GABA to support abstinence and is dosed three times daily, cleared by the kidneys, and preferred if you have liver issues. Some patients benefit from combination therapy.
Both block opioid receptors, but naloxone acts within minutes and is used to reverse opioid overdoses. Naltrexone is longer-acting and used for maintenance treatment of AUD and OUD after detox. Naloxone is an emergency antidote; naltrexone is a preventive therapy.
Nalmefene is another opioid antagonist used in some countries for as-needed dosing to reduce alcohol intake. Naltrexone has broader availability and more data in the U.S. Choice may depend on access, side-effect profile, and drinking pattern.
Naltrexone blocks opioids and requires full detox before starting; it suits highly motivated patients or those with reliable follow-up. Buprenorphine is a partial opioid agonist that suppresses cravings and withdrawal without full euphoria and can be started sooner. Retention in treatment is often higher with buprenorphine.
Naltrexone is an antagonist requiring opioid-free initiation and provides blockade without opioid effects. Methadone is a full agonist given in structured programs, highly effective for retention and overdose reduction. Selection depends on patient preference, access, and clinical risks.
Suboxone combines a partial agonist with naloxone to deter misuse; it reduces cravings and withdrawal and is flexible for outpatient care. Naltrexone provides opioid blockade and suits people preferring non-agonist therapy or after completing agonist taper. Both reduce relapse and overdose when used properly.
Oral tablets are inexpensive and flexible but require daily adherence. The monthly injection ensures continuous blockade, improves adherence, and avoids daily decisions, but needs clinic visits and can’t be quickly reversed if side effects occur.
Naltrexone directly blunts alcohol’s reward and is FDA-approved for AUD. Topiramate is off-label, may reduce heavy drinking via GABA/glutamate pathways, but can cause cognitive side effects and tingling. Naltrexone is typically first-line; topiramate is a consideration when first-line options aren’t tolerated.
Naltrexone is approved for AUD and reduces reward. Gabapentin is off-label, may help with sleep, anxiety, and protracted withdrawal and can reduce drinking in some, but misuse potential exists. They can be combined under supervision.
Naltrexone has stronger evidence for reducing heavy drinking. Baclofen, a GABA-B agonist, is off-label; it may aid abstinence in some, especially with liver disease, but data are mixed and sedation is common. Choice depends on liver status, side effects, and goals.
Naltrexone alone is not a weight-loss drug. Contrave pairs naltrexone with bupropion to influence appetite pathways and is approved for chronic weight management alongside diet and exercise. Use Contrave only if weight loss is the goal and alcohol/opioid-related considerations are addressed.
