Kranzler 2009: targeted naltrexone for people cutting down

What they tested

Participants got naltrexone 50 mg or a placebo (a dummy pill). Some were told to take it every day, others to take it only in situations they identified as high-risk for heavy drinking. Everyone's goal was to drink within safe limits, not to stop completely.

Each day, participants phoned an automated system to report how much they drank and whether they took their medicine. The researchers checked whether results differed between men and women.

What they found

On the main measure, average drinks per day, men in the targeted naltrexone group drank significantly less at week 12 than people in the other groups. This advantage was seen in men, not women.

On drinks per drinking day, a secondary measure, the targeted naltrexone group drank significantly less than the other groups during week 12, and this time the effect didn't depend on sex.

The authors wrote that the results support a targeted approach for heavy drinkers, particularly men, but argue for adding other strategies or using more effective medicines than naltrexone to get a bigger effect.

Limits

• The main benefit showed up in men only, and the trial wasn't large enough to say much about each subgroup.
• Results are reported at week 12, so the abstract says nothing about what happens after treatment ends.
• Drinking was self-reported by phone, which depends on people answering honestly every day.

What it means if you're considering naltrexone

This trial was set up to repeat an earlier finding that taking naltrexone ahead of risky situations helps people cut down. It supports the idea that as-needed naltrexone can reduce drinking, especially in men, which is relevant to anyone considering a targeted or Sinclair-style approach.

The authors themselves were cautious: they described the effect as needing a boost from other strategies or better medicines. The site's guide on dosing lists this trial as one of two US tests of targeted use.