In Health Watch:People who struggle with cocaine addiction often try for years to kick the habit.Now, some addicts are helping test a new kind of therapy... a pill... To help them overcome their dependency.Wendy Rigby has the story.It's illegal.It's expensive.And it's extremely addictive.Cocaine is an illicit drug used by an estimated 20-thousand people in San Antonio alone.This man, who chooses to conceal his identity, was one of them.He first used cocaine at age 10.He says, 'by the time I was 12 I knew I was addicted. When you're doing cocaine, you always think you can stop. You feel like you can. Until it's all gone and then you feel like that you can't.'Now, he's part of a study at the u-t health science center to test this pill...a drug called "vigabatrin" made by catalyst pharmaceuticals.Dr. John Roache says, "the brain stem's coming up here..."The medication is designed to work on brain chemicals, dampening the drug's pleasurable, rewarding sensation and cutting down on cravings.Dr. John Roache says, "The drug user feels a hunger or a thirst for drugs that can only be satisfied by taking the drugs. And so the medications are trying to alter that neuro-circuitry."Up until now, there's been no medical intervention for cocaine addicts.The man we talked to used to spend 160 dollars a day to feed his habit.Now, with the help of the pills under study, he's hoping to walk away from a 30-year drug habit.Patient says, 'I could tell that I was getting effect by the third day of taking the pills. I knew that the medication was there. You don't have the craving for it because your brain says "hey, we didn't have such a good party.""Vigabatrin" is used to treat epilepsy in Europe.Doctors here are hoping it will be effective for thousands of people hooked on cocaine, and they need more volunteers to test it.Dr. John Roache says, "We know there's a biology to the addiction and so what we're searching for is the medication that can address that biology. It's not just a matter of making up your mind."If this medication works for cocaine addiction, doctors hope it may prove effective for methamphetamine dependency as well.