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Research Summary

PRN Nalmefene: Can It Reduce Heavy Drinking?

Opioid antagonists may have a role in treating alcohol dependence. But, the optimal setting (primary care versus specialty treatment) and dosing regimen (scheduled versus as-needed [PRN]) are unclear.

Researchers in Finland randomized 403 heavy drinkers* from various sites (e.g., specialty treatment, private general practice) to the long-acting opioid antagonist nalmefene (10–40 mg) or to placebo to be taken PRN 1–2 hours before expected alcohol use. After 28 weeks, good responders in the nalmefene group were randomized to continue on nalmefene or to placebo for an additional 24 weeks.

  • Sixty percent of the nalmefene group and 68% of the placebo group completed the initial 28 weeks. On average, the nalmefene group took a pill on 35% of days, and the placebo group took a pill on 44% of days.
  • Over the initial 28 weeks, the risk of heavy drinking days (HDDs)** was 32% lower in the nalmefene group than in the the placebo group.
  • Among good responders to nalmefene at 28 weeks, those who continued nalmefene had a lower mean proportion of HDDs than did those who switched to placebo (18% versus 30%).
  • The most common side effects of nalmefene were nausea, insomnia, fatigue, and dizziness.


This research focused on harm reduction; subjects were not given specific abstinence or drinking goals and received minimal psychosocial intervention. In this context, PRN nalmefene showed promise for reducing heavy drinking days. The PRN schedule for nalmefene is intriguing. It would be interesting to learn more about the reasons for which individual subjects used the drug (e.g., to stem craving, to limit the number of drinks in a drinking session).

Kevin L. Kraemer, MD, MSc

*Self-reported difficulty controlling drinking plus at least 18 heavy drinking days and no more than 14 consecutive abstinent days in the last 12 weeks
**≥5 drinks per day for men, ≥4 for women


Karhuvaara S, Simojoki K, Virta A, et al. Targeted nalmefene with simple medical management in the treatment of heavy drinkers: a randomized double-blind placebo-controlled multicenter study. Alcohol Clin Exp Res. 2007;31(7):1179–1187.