Substance guides

What is Vivitrol? The monthly naltrexone injection explained

Published March 28, 2025 · 7 min read · Updated April 2026

Reviewed for accuracy by licensed clinical professionals.

Vivitrol is a once-monthly injection of extended-release naltrexone. It blocks opioid receptors, reducing cravings and the effects of opioids and alcohol.

How it works

Naltrexone is an opioid antagonist that blocks mu-opioid receptors. For opioids: prevents any opioid from producing effects (blocks the high). For alcohol: reduces the pleasure from drinking, gradually weakening the desire to drink.

Who it is for

People with opioid use disorder who have completed detox (must be opioid-free 7-14 days). People with alcohol use disorder (no detox requirement). Those who prefer monthly dosing over daily medication. Those who want no abuse potential in their medication.

What to expect

Monthly injection at a healthcare provider's office. Injection site reactions are common (pain, hardness) but manageable. Cannot use opioid medications while on Vivitrol. If you try to override the opioid block with high doses, overdose risk is extreme.

Authoritative sources

This article references guidelines from: SAMHSA · NIDA · ASAM

Frequently asked questions

What is Vivitrol?

A monthly injection of naltrexone that blocks opioid effects and reduces alcohol cravings.

How long do you take Vivitrol?

Duration varies. Many patients benefit from 6-12 months or longer. Discuss with your prescriber.

Does Vivitrol stop cravings?

It significantly reduces opioid and alcohol cravings. Most patients report decreased desire to use.

Disclaimer: Informational only. Not medical advice. SAMHSA: 1-800-662-4357.