A new study in rats has found that N-acetylcysteine (NAC), a commonly available and generally nontoxic amino acid derivative, reverses changes in the brain's circuitry associated with cocaine addiction. The reversal appears to lessen the cravings associated with cocaine, thus providing protection against relapse.

The findings were presented at Neuroscience 2009, the annual meeting of the Society for Neuroscience and the world's largest source of emerging news about brain science and health.

"Our finding suggests a promising therapeutic strategy for cocaine addiction, for which there is no approved treatment," said lead author Khaled Moussawi of the Medical University of South Carolina in Charleston.

Cocaine is a highly addictive drug characterized by frequent relapses. Recent advances in brain imaging are helping scientists uncover what happens in the brain when an addicted person is exposed to the drug-associated "cues" that trigger craving -- and lead to relapse. They've found that repeated exposure to psychoactive drugs such as cocaine causes an imbalance in the brain circuits regulating reward and cognitive control.

One of these circuits is a pathway involving the neurotransmitter glutamate. In the current study, Moussawi and his colleagues found that NAC restored normal functioning to this circuit in rats that had been previously addicted to cocaine. In addition, after receiving NAC, the previously cocaine-addicted rats did not reengage in drug-seeking behavior, even in the presence of drug-associated cues.

"Clinical trials involving people addicted to cocaine and nicotine have already suggested that N-acetylcysteine may be useful in decreasing cravings for those drugs," said Moussawi. "Our research adds support to that suggestion." A phase III clinical trial using NAC to treat cocaine addiction is currently underway.

Research was supported by the National Institute of Drug Abuse.