O'Malley 2002: naltrexone cut craving and drinks in a lab session

What they tested

Eighteen people with alcohol dependence who weren't looking for treatment were randomly given naltrexone 50 mg or a placebo for 6 days. On day 6 they had a starter drink meant to raise blood alcohol to 0.03 g/dl.

For the next 2 hours they could have up to eight more drinks, each designed to raise blood alcohol by 0.015 g/dl, or take US $3 for each drink they turned down. Researchers also measured craving and stress hormones.

What they found

Before any alcohol, people on naltrexone had higher levels of cortisol, a stress hormone, and less craving than those on placebo.

Responses to the starter drink didn't differ. After it, people on naltrexone drank fewer drinks, drank them more slowly and reported less craving.

Naltrexone also raised levels of the hormones ACTH and cortisol, part of the body's stress-hormone system. Higher cortisol went with less craving, and more craving went with more drinks chosen. Nausea ratings were low and no different between the groups.

Limits

• It was a very small lab study, and the volunteers weren't seeking treatment, so it may not reflect patients in a clinic.
• A 2-hour lab session with money on offer is a model of drinking, not a measure of drinking in daily life.
• The link between stress hormones and craving is an association, and the authors present it as a hypothesis.

What it means if you're considering naltrexone

This study shows one way naltrexone may work: it doesn't change how the first drink feels, but it seems to lower the pull toward the next ones. Someone starting naltrexone may notice the effect less in the first drink than in wanting fewer after it.