Some patients given an experimental cocaine vaccine were able to substantially reduce their use of the drug, according to research funded by the National Institute on Drug Abuse (NIDA).

In the study, 115 cocaine-using patients enrolled in a methadone maintenance program were given either the vaccine or a placebo over a 12-week period, then tracked for another 12 weeks. Participants received relapse-prevention counseling and had their blood tested for the presence of cocaine; urine tests also were used to screen for cocaine and opiate use.

The vaccine works by stimulating the immune system to create anti-cocaine antibodies that attach themselves to cocaine molecules in the blood, making them too large to pass into the brain. Researchers found that 38 percent of subjects were able to produce antibodies in sufficient amounts to block cocaine's effects, and of these, 53 percent were abstinent more than half the time during the study period, compared to 23 percent of the control group.

The high-antibody group also had more cocaine-free urine samples overall than those who received the placebo or generated lower levels of antibodies. "In this study immunization did not achieve complete abstinence from cocaine use," said lead researcher Thomas Kosten, M.D., of the Baylor College of Medicine. "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," said NIDA Director 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."

The study was published in the October 2009 issue of the Archives of General Psychiatry.