An old treatment is making a comeback in the battle against alcoholism. Scientists have made a simple change in a drug used to curb cravings, and it's making a big difference in its success. But there's a catch. With this new version, early research suggests it only works in men.

It is the most commonly consumed drug in this country. But like any drug, alcohol has side effects. One of the most frightening is addiction. It's estimated that men make up two thirds of the country's alcohol dependent population.

Now, an experimental treatment is showing promise in helping some battle their addiction. It's an injectable version of the drug Naltrexone, which works by blocking brain chemicals that trigger the euphoria from drugs and alcohol. An older version of Naltrexone has shown some success in curbing cravings in alcoholics. But it's a pill and only works if patients take it every day.

Several studies showed it didn’t have as strong of an effect in most of the patients, and they stopped taking the medication after a couple of months. The Naltrexone injection may help overcome that hurdle because its effects last an entire month.

A study of more than 600 men and women found the injection curbed heavy drinking in men by nearly 50-percent compared to a placebo. Unlike the pill version, the Naltrexone shot had no effect on women, which puzzles researchers. They are hoping a large national study now underway will provide some answers.

The Naltrexone injection could be up for FDA review as early as next year. The drug will be marketed under the name Vivitrex and is also being tested as a treatment for drug addiction. The only real side effect of the Naltrexone injection was pain at the injection site.

It's estimated that up to 18 million people in the U.S. suffer from alcohol dependence or abuse. Alcohol abuse is the cause of more than 100,000 deaths in America each year and costs Americans a total of $1844.6 billion annually. (Sources: National Institute on Alcohol Abuse and Alcoholism and The National Institute on Drug Abuse)