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October 19, 2009
Cocaine Vaccine Shows Promise for Treating Addiction
Immunization with an experimental anti-cocaine vaccine results in a significant reduction in cocaine use, according to a clinical trial. The result is the first successful demonstration to date of a vaccine against an illegal drug of abuse.
Dr. Thomas Kosten, with a team at the Yale University School of Medicine, developed the cocaine vaccine and previously demonstrated its safety. Like vaccines against infectious diseases, the anti-cocaine vaccine stimulates the immune system to produce antibodies. The antibodies attach themselves to cocaine molecules in the blood and prevent them from passing through the blood-brain barrier. By preventing the drug's entry into the brain, the vaccine inhibits or blocks cocaine-induced euphoria.
A team led by Kosten, now at the Baylor College of Medicine in Houston, recently carried out a clinical trial to test the vaccine's efficacy, with funding primarily from NIH's National Institute on Drug Abuse (NIDA). The trial included 115 patients from a methadone maintenance program who were randomly assigned to receive the anti-cocaine vaccine or a placebo (inactive) vaccine. The participants received 5 vaccinations over a 12-week period and were followed for an additional 12 weeks. All attended weekly relapse-prevention therapy sessions with a trained substance abuse counselor. The patients had their blood tested for antibodies to cocaine and their urine tested for the presence of opioids and cocaine.
In the October 2009 issue of the Archives of General Psychiatry, the scientists reported that participants who generated the highest antibody levels in response to the vaccination had the greatest reductions in cocaine use. Thirty-eight percent attained blood levels of anti-cocaine antibodies thought to be sufficient to block cocaine's euphoric effects. During weeks 9 to 16 (when antibody levels peaked), these participants had significantly more cocaine-free urine samples (45%) than those who received the placebo or those with active vaccine but low levels of antibodies (35%). The researchers saw no serious adverse effects from the vaccinations.
“In this study, immunization did not achieve complete abstinence from cocaine use,” Kosten says. “Previous research has shown, however, that a reduction in use is associated with a significant improvement in cocaine abusers' social functioning and thus is therapeutically meaningful.”
“The results of this study represent a promising step toward an effective medical treatment for cocaine addiction,” says NIDA Director Dr. Nora Volkow. “Provided that larger follow-up studies confirm its safety and efficacy, this vaccine would offer a valuable new approach to treating cocaine addiction, for which no FDA-approved medication is currently available.”