Naltrexone (Vivitrol, ReVia): oral

What it treats

Oral naltrexone is approved by the U.S. Food and Drug Administration for alcohol use disorder and opioid use disorder. In alcohol use disorder, it's used to reduce heavy drinking days and to quiet the reward that alcohol produces. In opioid use disorder, it's used after detox to prevent relapse by blocking the effect of opioids.

Clinicians reach for it when someone wants a non-controlled medication, when abstinence from opioids has been achieved and needs to be held, or in alcohol use disorder as a first-line option alongside acamprosate. It doesn't require special DEA registration beyond a standard license and any prescriber can write for it.

How it works

Naltrexone binds tightly to opioid receptors in the brain but doesn't turn them on. It occupies the receptor so that if someone drinks alcohol, the reward pathway (which depends partly on the body's own opioid-like chemicals) is quieter. If someone uses opioids, the drugs can't produce their usual effect.

The full story on why this reduces heavy drinking isn't perfectly worked out. The likely mechanism is that alcohol triggers release of endogenous opioids, and blocking that reward makes drinking feel less compelling over time.

Receptor mechanism (detail)

Naltrexone is a competitive antagonist at the µ-opioid receptor, with weaker activity at κ and δ receptors. Because it occupies the receptor without activating it, endogenous opioids and any exogenous opioids (heroin, oxycodone, hydrocodone, and so on) can't produce their usual effect while naltrexone is on board.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

The standard dose is 50 mg once a day, taken by mouth. Some clinicians use 25 mg for the first day or two to test tolerability. Doses up to 100 mg have been studied, but the 50 mg dose is what's on the label.

A negative urine drug screen for opioids and an opioid-free window of 7 to 10 days (longer for methadone or buprenorphine) is required before the first dose. Some clinicians use a naloxone challenge test in higher-risk situations before starting.

Safety monitoring

• Liver function tests (LFTs) at baseline and periodically. Naltrexone can cause hepatotoxicity, and existing liver disease matters.
• Opioid-free confirmation before the first dose. Urine drug screen and a careful history of last opioid use.
• Overdose risk after stopping. Tolerance to opioids drops while on naltrexone. If someone relapses after discontinuing, a dose that was survivable before can now be fatal.
• Adherence. For the oral form, taking it every day is the hardest part.
• Mood. Some people report low mood or feeling flat on naltrexone. Worth asking about.

What to expect

Common side effects

• Nausea, especially in the first days.
• Headache.
• Fatigue.
• Dizziness.
• Trouble sleeping or vivid dreams.
• Abdominal discomfort.
• Low mood or feeling flat in some people.

Nausea is the most common. Taking it with food often helps.

Serious side effects and warnings

• Hepatotoxicity. Naltrexone can cause liver injury, especially at higher doses. LFTs at baseline and periodically catch most problems early. New right-upper-quadrant pain, jaundice, or dark urine needs prompt attention.
• Precipitated opioid withdrawal. If naltrexone is given while opioids are still on board, it can trigger severe, rapid withdrawal that's hard to manage.
• Loss of tolerance and overdose. After stopping naltrexone, opioid tolerance is lower than it used to be. A relapse dose that would once have been tolerated can be fatal. A naloxone kit at home matters.
• Depression and suicidality. Uncommon but reported. Worth watching for.

Sexual and relational effects

Sexual side effects aren't a prominent feature of naltrexone, though some people report reduced libido or delayed orgasm. More often, the relational conversation is about recovery: partners, family, and sponsors as part of a support system. Being on naltrexone doesn't remove the work of building relationships without alcohol or opioids at the center. If sexual function shifts after starting, that's worth raising with the prescriber.

Weight, appetite, and sleep

Weight change on naltrexone is usually modest. Appetite can dip early because of nausea. Sleep can be disrupted in the first weeks, sometimes with vivid dreams. Most of this settles.

Starting and dosing basics

This section is general background, not a dosing instruction for any individual.

Before the first dose, a full opioid-free window matters: usually 7 to 10 days from short-acting opioids and longer for methadone or buprenorphine. A urine drug screen and a careful history help confirm. Some clinicians do a naloxone challenge in higher-risk cases. Once started, the pill is taken daily, often in the morning, with or without food.

Missed doses and interactions

If a dose is missed, take it when remembered unless the next dose is close. Don't double up.

The big interaction is with opioids of any kind. Prescription pain medications, cough syrups with codeine, and street opioids will either not work or will need to be given at higher risk. Any surgery or dental work needs the treating team to know that naltrexone is on board. A medical alert card or bracelet can help in an emergency.

Alcohol interactions aren't dangerous the way disulfiram is, but drinking on naltrexone often feels less rewarding. At high doses, alcohol still causes its usual problems (impaired driving, overdose, aspiration), so this isn't a free pass.

Stopping and tapering

Naltrexone doesn't cause physical dependence, so there's no medical withdrawal from stopping it. The bigger issue is what happens if opioid use resumes. After a period on naltrexone, tolerance is reduced, and the risk of overdose from a previously familiar dose is high. Any plan to stop should include a relapse-prevention plan and a naloxone kit at home.

Pregnancy and breastfeeding

Data on naltrexone in pregnancy is limited. It does cross the placenta and enters breast milk in small amounts. The decision belongs with a clinician who knows the person's situation, weighing the risks of continued substance use against those of the medication.

Anyone who is pregnant, planning a pregnancy, or breastfeeding should talk it through with a prescriber.

Cost and generic availability

Oral naltrexone has been available as a generic for years and is inexpensive. The brand name is ReVia (Depade is another older brand). Generic naltrexone contains the same active medication and works the same way.

Common questions

How long does it take to work? For alcohol use disorder, some people notice within a couple of weeks that drinking is less rewarding. Steady benefit builds over one to three months. Adherence and counseling matter.

Can I drink on this? Physically, drinking on oral naltrexone isn't dangerous the way it is with disulfiram. But the medication is designed to make alcohol less rewarding, and reducing or stopping drinking is the whole point.

Is it addictive? No. Naltrexone doesn't produce a high and isn't controlled.

What if I need pain medication? Opioid pain medications won't work while naltrexone is on board. For surgery or serious injury, the plan needs to be talked through with the treatment team in advance. Non-opioid pain approaches are the default.

What if I relapse to opioids while on it? The opioid effect will be blocked, but if very large doses are used to try to override the block, dangerous respiratory depression can happen. Also, after stopping naltrexone, tolerance is reduced, so a previously familiar dose can be fatal.

Questions to ask your prescriber

• What are we hoping this treats, and how will we know it's working?
• How long should I plan to stay on it?
• What's the plan if I have pain or need surgery?
• What signs would tell you it isn't the right medication for me?
• Should I have naloxone at home in case of a relapse?

Sources

This guide draws on current prescribing information and public health references. It is reviewed for clinical accuracy and updated as guidance changes, and current as of June 8, 2026.

• U.S. Food and Drug Administration. Naltrexone (ReVia) prescribing information.
• MedlinePlus, U.S. National Library of Medicine. Naltrexone.
• National Institute of Mental Health. Mental health medications.
• American Society of Addiction Medicine. Alcohol Use Disorder and Opioid Use Disorder guidelines.
• DailyMed, U.S. National Library of Medicine. Naltrexone hydrochloride tablets.