O'Malley 2000: who gets nausea on naltrexone

What they tested

After 5 to 30 days without alcohol, 120 people with alcohol dependence took naltrexone 25 mg for the first dose and then 50 mg daily for 10 weeks. Everyone knew they were taking naltrexone.

After 1 week, new side effects were rated mild, moderate or severe. The researchers then used statistics to see which traits before treatment predicted moderate to severe nausea. They expected recent and heavy drinking to matter, because of how long-term alcohol use may change the body's own opioid system.

What they found

Moderate to severe nausea was reported by 18 people (15%) and was linked to poorer pill-taking and heavier drinking during treatment.

Age, sex, how heavily people drank, how long they had been abstinent, and the combination of the last two all predicted nausea. Younger people and women had higher rates.

The pattern depended on recent drinking. With shorter abstinence, lighter drinkers were more likely to have nausea than heavier drinkers. With longer abstinence the risk fell, especially for lighter drinkers.

Limits

• There was no placebo group, so some of the nausea may not have been caused by naltrexone.
• Nausea was rated only after the first week.
• The predictors are links found in one group of 120 people, not tested by random assignment.

What it means if you're considering naltrexone

Nausea is the side effect most likely to make people give up on naltrexone, and this study suggests it isn't random. Younger people, women and people who have only just stopped drinking were more likely to get it. The paper discusses ways to lower the risk, and those are worth talking through with a prescriber, but this abstract doesn't spell them out.