McCaul 2000: naltrexone made alcohol less likeable for heavy drinkers

What they tested

Each of 23 heavy drinkers was maintained on naltrexone at 0 (placebo), 50 and 100 mg a day at different times. Under each dose they were given no alcohol, a moderate amount or a high amount.

Researchers measured how people felt, including liking, sedation and desire to drink, and their performance on coordination and reaction tests.

What they found

Even before drinking, people reported less desire for alcohol on 50 mg than on placebo.

After drinking, naltrexone significantly increased ratings of sedation and of unpleasant or sick feelings, and lowered ratings of liking, best effects and desire to drink.

Naltrexone generally did not change subjective or objective signs of drunkenness. The biggest drops in liking and best effects came when the high naltrexone dose was combined with the high alcohol dose.

Limits

• It was a small lab study, and the abstract doesn't say whether participants were seeking treatment.
• Lab drinking sessions don't show whether these changes lead to less drinking over months.
• The 100 mg dose is higher than the usual tablet dose for alcohol.

What it means if you're considering naltrexone

This study helps explain how naltrexone may work in people who keep drinking: alcohol becomes less enjoyable and more sedating, and the urge for more drinks drops. It also shows what naltrexone doesn't do. People were just as drunk, so it offers no protection against impairment, and driving after drinking is no safer on it.

The authors suggested naltrexone may be most useful for patients who continue to drink heavily, which fits the idea behind taking it while still drinking.