Naltrexone, approved for the treatment of alcohol dependence, also helps heavy social drinkers who aren't alcoholics to quit smoking, as well as to reduce the amount of alcohol they drink, a new study shows.

After taking naltrexone, smokers who were heavy drinkers had significant reductions in heavy drinking rates over the course of the 8-week treatment, and also were more likely to quit than heavy drinkers taking placebo, lead investigator Dr. Andrea C. King told Reuters Health. "The effects were not as prominent among the lighter drinking smokers," she noted.

Smokers who are also regular drinkers are a "historically treatment-resistant group in smoking cessation," King and colleagues at the University of Chicago point out in their paper, published in the current issue of Alcoholism: Clinical & Experimental Research. "Since alcohol drinking may increase urges to smoke and precipitate smoking lapses, it would follow that naltrexone might be beneficial for drinker-smokers."

To investigate, the study team examined the alcohol consumption and liver enzyme levels (an objective biomarker used to confirm self-reported drinking, as well as a liver safety indicator) in 78 nonalcoholic social-drinking smokers enrolled in a larger study looking at the effectiveness of naltrexone on smoking cessation.

Thirty-four patients were randomly assigned to receive naltrexone and 44 to a placebo. Naltrexone (25 mg daily) or placebo was started 3 days prior to the quit date and continued at 50 mg daily for 8 weeks.

"Naltrexone, at 50 mg oral daily, when added to counseling and (nicotine) patch, significantly decreased heavy drinking rates in smokers enrolled in smoking cessation," King noted in a statement.

"Among heavy drinkers only, naltrexone tended to yield higher smoking quit rates compared with placebo (80 percent vs. 52 percent)," the team reports.

Overall, subjects with the heaviest drinking patterns appeared to benefit the most from naltrexone, in terms of alcohol and smoking outcomes, likely due to the strong interconnections between drinking and smoking for many individuals, the researchers note.

Compared to placebo, naltrexone treatment in this subgroup of relatively healthy nonalcoholic nicotine-dependent patients did not produce increases in the two liver function enzymes aspartate aminotransferase or alanine transaminase levels, which supports the hepatic safety of naltrexone in smokers, the researchers say.

If these findings are supported in a larger sample, "then use of naltrexone could be expanded to drinkers-smokers who are trying to quit smoking," King said.