WASHINGTON – Bar-hoppers everywhere discovered long ago that smoking and drinking go hand-in-hand.

So, why not a single pill that helps curb the two vices?

A drug called varenicline may be the answer. The tablets already have been shown to make smoking less rewarding for some. Preliminary work, done in rats, suggests they could do the same for drinking.

“The biggest thrill is that this drug, which has already proved safe for people trying to stop smoking, is now a potential drug to fight alcohol dependence,” said Selena Bartlett, a University of California, San Francisco neuroscientist who led the study. Details appear this week in the journal Proceedings of the National Academy of Sciences.

That a single drug could work to curb both addictions isn’t a given – nor is it surprising, said Christopher de Fiebre, an associate professor of pharmacology and neuroscience at the University of North Texas Health Science Center at Fort Worth.

“This is an extremely important paper and hopefully it will convince the major funding agencies that they need to examine the interactions between nicotine and alcohol to a greater extent than they have done to date,” said de Fiebre, who was not connected with the study.

Pfizer Inc. developed varenicline specifically as a stop-smoking aid and has sold it in the United States since August under the brand name Chantix. Pfizer provided the drug for the new study, but was not otherwise involved in the research.

Varenicline works by latching onto the same receptors in the brain that nicotine binds to when inhaled in cigarette smoke, an action that leads to the release of dopamine in the brain’s pleasure centers. Taking the drug blocks any inhaled nicotine from reinforcing that effect.

The new study suggests not just nicotine but alcohol also acts on the same locations in the brain. But several experts not involved in the study cautioned that there is no such thing as a magic cure-all for addiction and that varenicline and similar drugs may find more immediate use in treating diseases like Alzheimer’s and Parkinson’s.

Expanding its use as a treatment for alcohol abuse may be the first order of business, though. The University of California researchers, together with the National Institute on Alcohol Abuse and Alcoholism, are now planning the first studies in humans of the drug’s effectiveness in curbing alcohol cravings and dependence, Bartlett said. That the drug is already Food and Drug Administration-approved should speed things along.

“This is a drug that people are actually using. That’s not trivial – not at all,” said Mark Egli, co-leader of the medications development program at the NIAAA, part of the National Institutes of Health. “There is plenty of animal research that looks pretty cool but there is no way those drugs are ever going to be used by human beings.”

In the new study, researchers trained rats to drink alcohol and measured the effect of varenicline once the animals became the laboratory equivalent of heavy drinkers. They found the drug curbed their drinking. Even when stopped, the animals resumed drinking but didn’t binge.

Just as varenicline doesn’t work for all smokers, it’s highly unlikely it would for all drinkers.

“Is this going to be a cure-all? No, not for smoking or alcoholism because both diseases are more complicated than a single target or single genetic issue,” said Allan Collins, a professor of pharmacology at the University of Colorado who was not connected to the study.