Naltrexone for Alcohol: How It Works

Naltrexone is an opioid antagonist, FDA-approved for alcohol use disorder since 1994. That description is accurate and almost useless, so here is what it means in practice.

The mechanism, plainly

Drinking triggers a release of endorphins that bind to opioid receptors in the brain. That binding produces much of alcohol's rewarding quality — and, importantly, it is a large part of why the second drink feels more compelling than the first did.

Naltrexone occupies those receptors without activating them. The endorphins released by drinking have nowhere to bind, so the reward is blunted. Over repeated occasions, the association between drinking and reward weakens.

People rarely describe this as dramatic. The common description is that the pull is quieter — stopping after one or two stops feeling like a fight.

What it is not

• Not a controlled substance. No high, no withdrawal on stopping.
• Not a sedative. It does not affect energy, mood, or functioning.
• Not disulfiram. It will not make you ill if you drink.
• Not permanent. Many people take it six to twelve months.

The first few weeks

Common side effects — mild nausea, headache, sometimes disrupted sleep — are most noticeable early and usually settle within one to two weeks. Taking the dose with food often helps. If side effects persist or are severe, that is a reason to speak to your provider rather than to stop quietly.

Expectations matter here. Naltrexone does not remove the desire to drink on day one. What people more often notice, a few weeks in, is that an occasion they would normally have found hard passed without much struggle.