What Is Naltrexone?

The Short Answer

Naltrexone is an FDA-approved prescription medication that blocks opioid receptors in the brain. It has been approved for the treatment of alcohol use disorder since 1994 and for opioid use disorder since 1984. It is not an opioid, it is not addictive, and it does not produce euphoria.

How Naltrexone Works

Naltrexone is an opioid receptor antagonist. It works by binding to opioid receptors in the brain and blocking them — preventing opioids (including the endorphins released by alcohol) from producing their normal effects.

When you drink alcohol, the brain releases endorphins that bind to opioid receptors and produce a rewarding effect. Naltrexone blocks this process. The alcohol is still consumed, but the brain does not receive the expected reward signal.

FDA-Approved Uses

• Alcohol use disorder — approved 1994 (oral naltrexone); extended-release injectable naltrexone (Vivitrol) approved 2006
• Opioid use disorder — approved 1984

Forms of Naltrexone

• Oral naltrexone (50mg tablet) — the most common form used in the Sinclair Method
• Extended-release injectable (Vivitrol) — monthly injection, typically used for abstinence support
• Low-dose naltrexone (LDN) — used off-label for various conditions; different from standard dosing

Is Naltrexone Addictive?

No. Naltrexone is not an opioid and does not produce euphoria or dependence. It is not a controlled substance. See Is Naltrexone Addictive? for a full discussion.

Important Safety Information

Naltrexone is not appropriate for everyone. It requires a medical evaluation before prescribing. Key contraindications include current opioid use, significant liver disease, and acute hepatitis. See Naltrexone Side Effects and Questions to Ask a Doctor for details.