Cocaine addiction is focus of nationwide research
When baseball player Darryl Strawberry said he had no idea why he had returned to cocaine use after being weaned from the drug, he may have been telling the truth, and his relapse may have been his body's unconscious response to a reward system built up in his brain during cocaine use.
This speculation and other laboratory findings from 10 years of research on cocaine's effect on the brain were discussed during a recent psychiatry grand rounds given by Dr. Frank J. Vocci, director of treatment research and development for the National Institute on Drug Abuse (NIDA). Dr. Vocci was the third distinguished lecturer in a series hosted by the psychiatry department's division of alcohol and drug addiction.
Cocaine, the central nervous system stimulant and topical anesthetic derived from the coca plant, is being snorted, smoked or injected regularly by an estimated 2 million Americans who are addicted to it. It gives them a quick high, with feelings of euphoria, but tapers off quickly into a depressed, irritable state.
Dr. Vocci described the wide range of drug testing and even vaccine development against cocaine that has been under way for the past decade at medical centers across the country, including UCLA, Johns Hopkins, the University of Pennsylvania and the Health Science Center. New work is being done at the UTHSC by Dr. Bankole Johnson, psychiatry, and his Southwest Texas Addiction Research and Technology (START) Center. The START Center is about to embark on two new clinical trials to determine the effectiveness of a novel compound against both cocaine and methamphetamine dependence.
"We are studying the neurobiology of addiction," Dr. Vocci said, "and we are trying to understand what cocaine is doing in the brain. We also are trying to develop drugs that can block those actions." Dr. Vocci described trials of drugs including Disulfiram, Selegiline, Amantadine, Desipramine and other of the 60 medications that have been extensively studied in recent years. "We have identified eight drugs that may show promise for treating cocaine addiction," he said.
Each of the eight shows some positive aspect. For example, Selegiline seems to blunt the high that users feel and there is a new 16-site trial starting this month that will deliver the drug through a skin patch. Desipramine, an antidepressant, seems to work best in depressed patients who are taking in the drug through the nose. Amantadine has been shown to be most effective in patients with the most severe dependence.
Other modulators of cocaine use can be stress and nicotine, which one study showed increased the desire for cocaine.
Dr. Vocci also discussed contingency management, a procedure in which subjects are paid to stop using cocaine. "It works!" he said. "We see a robust response to this method and that fact is a good example of how behavior can play an integral role in the action of these addicts."
Cocaine-induced changes in the brain do not seem to be simple and some changes may be permanent, the pharmacologist said. These might include changes during abstinence that make someone more susceptible to relapse. "As an analogy, think of a cucumber. You can change a cucumber into a pickle, but you can't change it back to a cucumber again," he said. "Maybe the brain undergoes changes during drug use that cannot be reversed by simply stopping."
Dr. Vocci discussed research on the dopamine system and the brain's ability to learn to expect a reward from certain behavior. He also discussed the depletion of dopamine caused by cocaine. "There are a series of biological effects from cocaine use. Addicts taking this drug use a different system for decision making than non-users. They think differently. The drug hijacks their brain."