More than 15 million Americans drink too much, according to the National Institute on Alcohol Abuse and Alcoholism. New research on rats may help them curb that addiction.

At present, there are three approved drugs for battling alcoholism, none of which work very well. Among them: naltrexone, which is effective for some alcoholics (as well as opiate addicts) because it blocks a pain pathway in the brain associated with the pleasures of drinking.

In an effort to boost its effectiveness, neuroscientist Selena Bartlett of the Ernest Gallo Clinic & Research Center at the University of California, San Francisco, and her colleagues chemically manipulated naltrexone so that it cut off a related pleasure pathway in the brain. Their findings, published in the journal Biological Psychiatry: rats (trained to crave alcohol) given the new compound, dubbed SoRI-9409, consumed half as much hooch. In addition, there were fewer side effects. Researchers say that unlike naltrexone, this drug did not diminish the animals' desire for water and other nonalcoholic beverages, such as sugar water. "It is much more selective in its effect on drinking," Bartlett says.

Rats given the drug for 28 days refrained from heavy drinking for another four weeks after they were taken off the drug. "That is currently the biggest challenge in alcoholism treatment," which relies primarily on rehabilitation centers, Bartlett notes. When people return home, they typically also return to drinking. "Drinking stays down without the drug in place. It's done something to permanently change and reduce the drinking."

Efficacy trials in humans are already ongoing for another drug known as varenicline, which, in addition to curbing smoking, also cuts drinking. But SoRI-9409 might prove more specifically focused on alcoholism as well as free of some of the side effects reported by those who use varenicline to stop their craving for nicotine.

"We've got a pipeline of different medications targeting different aspects of the disease," Bartlett says. "It's an exciting time for people that suffer from this disease as there are more treatments coming through. Once upon a time, this wasn't really considered possible."