Naltrexone is designed to prevent craving among people with alcohol dependence, but the drug appears to have the opposite effect on some patients, MedPages Today reported July 24.

Brown University researcher John McGeary, Ph.D., reported that some heavy drinkers who have a particular single nucleotide polymorphism (SNP) in one of their opiate receptor genes experienced strong cue-related cravings while taking naltrexone, compared to patients receiving a placebo. The SNP is at position 118 in the µ-opiate receptor gene (OPRM1).

"These results suggest that naltrexone, under certain circumstances, may increase rather than decrease the urge to drink alcohol, and that variation in the OPRM1 gene may be a moderator of naltrexone's effect on cue-elicited urge to drink," the researchers wrote.

McGeary's study also concluded that naltrexone did not effectively prevent craving among any of the patients studied -- all of whom were heavy drinkers and not currently seeking treatment. Past studies have found that naltrexone was effective with alcoholics seeking treatment.

The study appears in the August 2006 issue of the journal Alcoholism: Clinical & Experimental Research.

McGeary, J., Monti, P., Rohsenow, D., Tidey, J., Swift, R., & Miranda Jr., R. (2006). Genetic Moderators of Naltrexone's Effects on Alcohol Cue Reactivity. Alcoholism: Clinical & Experimental Research, 30(8): 1288-1296.