What Is Naltrexone? Uses, Dosage, and What You Need to Know in 2026

Naltrexone is one of only three FDA-approved medications for opioid use disorder and one of three FDA-approved medications for alcohol use disorder. Despite being available for over 40 years, it remains underused — partly due to stigma around addiction treatment, partly due to limited awareness. In 2026, with demand for addiction treatment growing and generic naltrexone facing supply challenges, understanding this medication has never been more important.

This guide answers the most common questions patients and their families have about naltrexone: what it is, what it treats, how to take it, and what to watch out for.

What Is Naltrexone?

Naltrexone is a prescription medication classified as an opioid antagonist. It works by binding to opioid receptors in the brain — the same receptors that produce feelings of pleasure and reward from opioids and, indirectly, from alcohol. By occupying these receptors, naltrexone blocks the "high" from opioids and dampens the pleasurable effects of alcohol.

Critically: naltrexone is not an opioid itself. It does not produce euphoria, does not cause dependence, and has no abuse potential. This makes it unique among addiction treatment medications — it is the only non-controlled, non-addictive option for both AUD and OUD.

What Is Naltrexone Approved to Treat?

The FDA has approved naltrexone for two conditions:

Alcohol Use Disorder (AUD): Naltrexone helps reduce cravings for alcohol and the pleasure of drinking, making it easier to cut back or stop drinking altogether. Both the oral tablet and the Vivitrol injection are approved for AUD.

Opioid Use Disorder (OUD): Naltrexone blocks the euphoric and sedative effects of opioids. The FDA specifically approved the extended-release injectable Vivitrol for OUD, and it is used to prevent relapse in patients who have already completed opioid withdrawal (detoxification). Patients must be opioid-free for at least 7-10 days before starting naltrexone to avoid precipitated withdrawal.

What Are the Off-Label Uses of Naltrexone?

Beyond its FDA-approved uses, naltrexone is prescribed off-label for several other conditions:

Low-dose naltrexone (LDN): At doses of 1.5-4.5 mg (much lower than the standard 50 mg), naltrexone is used off-label for fibromyalgia, multiple sclerosis, Crohn's disease, and other autoimmune conditions. LDN is not FDA-approved for these uses but is the subject of ongoing research.

Weight management: Naltrexone is combined with bupropion in the FDA-approved weight loss medication Contrave. Naltrexone alone is not FDA-approved for weight loss.

Impulse control disorders: Some research supports off-label use for gambling addiction and other compulsive behaviors, as these also involve the brain's opioid reward pathways.

What Forms Does Naltrexone Come In?

Naltrexone is available in two forms:

Oral tablet (50 mg, generic only): Taken once daily by mouth. Brand-name versions (ReVia, Depade) have been discontinued; only generic tablets are available. Cost: $32-$90/month with coupons.

Extended-release injectable (380 mg, Vivitrol): Administered once monthly by intramuscular injection by a healthcare provider. No generic equivalent available. Cost: $1,200-$2,127/month without insurance (manufacturer copay program available).

How Is Naltrexone Taken?

For the oral tablet:

Standard dose: 50 mg once daily

Some providers start at 25 mg for 1-3 days to reduce initial nausea, then increase to 50 mg

Can be taken with or without food, but food reduces stomach side effects

Take at roughly the same time each day; timing can be adjusted based on side effects (morning if drowsy, evening if it causes insomnia)

For Vivitrol:

380 mg intramuscular injection administered every 4 weeks by a healthcare provider

Injected into the upper outer quadrant of the gluteal muscle

Cannot be self-administered — must be done in a clinical setting

What Are the Most Important Things to Know Before Starting Naltrexone?

For OUD patients: You MUST be opioid-free for at least 7-10 days (short-acting opioids) or 10-14 days (long-acting opioids/methadone) before starting naltrexone. Starting too early causes severe precipitated withdrawal.

Liver health: Naltrexone has a boxed warning for hepatotoxicity at high doses. Your provider will check liver function tests before starting and monitor periodically.

Opioid medications: Naltrexone blocks all opioids — including pain medications. Tell every healthcare provider you see that you are taking naltrexone, especially before surgery or emergency care.

Counseling: Naltrexone is most effective when combined with counseling and behavioral therapy. It is a tool, not a cure.

Is Naltrexone a Controlled Substance?

No. Naltrexone is not a controlled substance and is not scheduled by the DEA. It has no abuse potential and cannot cause a high. This means any licensed prescriber — your primary care doctor, a nurse practitioner, or a telehealth provider — can prescribe it without special licensing. You can fill it at any regular pharmacy.

Finding Naltrexone in 2026

Naltrexone oral tablets are currently subject to an active shortage affecting some pharmacies. If you're having trouble finding naltrexone, medfinder.com can help by calling pharmacies near you to locate available stock and texting you the results.

Want to understand more about how naltrexone works in the brain? See: How Does Naltrexone Work? Mechanism of Action Explained in Plain English.