Half of the 55 alcoholics who took the anti-seizure drug topiramate either quit drinking altogether or cut back their drinking sharply.
Researchers found that those given the medication were six times more likely than those on a dummy pill to abstain from alcohol for a month, according to the report published Friday in The Lancet.
"This finding is a major scientific advance in the treatment of alcoholism," said Dr. Domenic Ciraulo, head of psychiatry at Boston University, who was not connected with the research.
Three drugs are now available worldwide for combating alcoholism. One of them, disulfiram, sold as Antabuse, makes people feel sick when they drink.
"The problem with that drug is that people know that if you want to drink, all you have to do is throw the tablet away. It is not a treatment. All it does is punish you for drinking," said Dr. Bankole Johnson, chief of alcohol and drug addiction research at the University of Texas Health Science Center at San Antonio and lead investigator in the latest study.
The other two drugs - acamprosate, available in Europe but not the United States, and naltrexone - are given to ward off relapses once an alcoholic has stopped drinking.
"What is good about topiramate is you can take it while you are still drinking," Johnson said.
Scientists believe that the brain chemical dopamine is what provides the pleasure from alcohol and that topiramate, sold as Topamax by Johnson & Johnson, works by washing away the excess dopamine released by drinking alcohol.
Long-term studies in epileptic patients show no serious problems related to topiramate.
The study involved 103 hardcore alcoholics followed for three months. Many had already tried methods such as Alcoholics Anonymous, medication, psychotherapy and rehab clinics. When they enrolled in the study it had been at least six months since they had been in treatment and they were drinking the equivalent of two bottles of wine a day.
Fifty-five drinkers were given topiramate, while 48 were given a dummy pill. The dose of topiramate was gradually increased.
All the participants got regular counseling to encourage them to keep taking the drugs and refrain from drinking.
By the time the study ended, 13 out of the 55 in the topiramate group, or 24 percent, had abstained continuously for a month. That compares with two out of 48 people, or 4 percent, in the placebo group.
"This is continuous abstinence. This is the strictest way of looking at it. You are not including people who may have had the odd drink," Johnson said.
The gap between the two groups was even wider when it came to binge drinking.
In the topiramate group, 28 out of 55, or 50 percent, did not binge in the final month, compared with 8 out of 48, or 16 percent, of those taking the fake pill. This means those taking the drug were nearly four times less likely to binge.
In the topiramate group, reported cravings were cut in half, compared to a 15 percent drop in the placebo group.
Ray Litten, chief of treatment research at the U.S. National Institute on Alcohol Abuse and Alcoholism, said topiramate could be a significant advance in treating alcoholism.
"It does look like topiramate might be stronger than naltrexone or acamprosate," Litten said. "It's very promising and it certainly has potential, but this is only one study and more trials need to be done."
Litten said a combination of drugs and psychological therapy is considered the best treatment.
"Alcoholism is a complex disease and there's no magic bullet out there," Litten said. "But just to get a menu of different treatments is a step in the right direction."
Many experts say abstinence should still be the goal, but Johnson argues that treatments that help alcoholics cut down - say, from 10 drinks a day to two a day - is worthwhile.
"If you can make most people stop drinking at a hazardous level, you have done them a power of good. You are going to improve these people's quality of life, help save their marriages, their jobs," Johnson said.
By Emma Ross