Mann 2016: how nalmefene works and how much it cuts drinking

What they tested

The authors reviewed how nalmefene works and ran a meta-analysis of published and unpublished trials aimed at reducing drinking, found through a systematic search. They measured changes in heavy drinking days and total daily alcohol from the start of each trial to its main endpoint.

Effects were expressed as Hedges' g, a standard measure of the size of the difference between nalmefene and placebo. Results were reported for everyone randomized and for the target population: people with a high drinking-risk level as defined by the World Health Organization.

What they found

In everyone randomized, nalmefene reduced heavy drinking days compared with placebo (Hedges' g = -0.20; 95% CI -0.30 to -0.09). In the target population of high-risk drinkers, the effect was larger (g = -0.33; 95% CI -0.48 to -0.18). Total alcohol consumption showed similar results.

On how it works, the authors describe nalmefene as blocking the mu- and delta-opioid receptors and partly activating the kappa-opioid receptor. Preclinical data suggest it counters changes that alcohol causes in the brain's endorphin and dynorphin systems.

They argue that aiming to drink less is an effective strategy that appeals to people who aren't ready to quit, and that because nalmefene doesn't require abstinence, it may draw more people into treatment.

Limits

• The site's nalmefene guide notes that one author was from Lundbeck, which markets nalmefene as Selincro.
• The abstract doesn't say how many trials or patients were pooled.
• The effect sizes were small, especially across everyone randomized.

What it means if you're considering naltrexone

Nalmefene is a close relative of naltrexone that this review says is approved in the European Union and other countries for cutting down drinking in high-risk drinkers. The review suggests its effect is real but small, and larger in heavier drinkers.

The site uses this review as context for the Sinclair Method. The as-needed approach has an approved form with nalmefene, but that doesn't mean the Sinclair Method itself is endorsed, and this review doesn't test naltrexone.