Tidey 2008: who naltrexone helps most in everyday drinking

What they tested

Everyone first took a placebo (a dummy pill) for 1 week. They were then randomly assigned to 3 weeks of naltrexone 50 mg a day or placebo.

Throughout, participants used palm-pilot computers to record in real time how much they drank, how strong their urges were, and how alcohol made them feel. The researchers looked at whether genes (DRD4 and OPRM1), family history of alcohol problems, age when alcoholism began, and gender changed naltrexone's effects.

What they found

Naltrexone reduced the percentage of drinking days across all participants.

It reduced the percentage of heavy drinking days only in people with the long form of the DRD4 dopamine receptor gene (DRD4-L).

Naltrexone lowered urges in people whose alcoholism began at a younger age, lengthened the time between drinks in people with more relatives who had alcohol problems, and reduced the stimulating effects of alcohol in women.

Variations in the OPRM1 gene, which codes for the receptor naltrexone blocks, did not change any of naltrexone's effects.

Limits

• Treatment lasted only 3 weeks.
• Participants weren't seeking treatment, so they may differ from people who go to a doctor for help with drinking.
• Many possible moderators were explored, which raises the chance that some subgroup findings happened by chance.

What it means if you're considering naltrexone

This trial adds evidence that naltrexone reduces drinking within a few weeks, measured in daily life rather than a clinic. The site's guide on how long naltrexone takes to work uses it as one of the closest data points on early effects.

The subgroup results are hints about who might respond more, not a way to predict an individual's response. The OPRM1 result is worth knowing because that gene codes for the receptor naltrexone blocks, yet it made no difference here.