Washington, Oct 6 : A new vaccine to treat cocaine dependence apparently has the potential to reduce drug use in people who attain high anticocaine antibody levels in response, according to a news study.

However, the research found that only 38 percent of vaccinated individuals went on to produce high enough antibody levels and those who did maintained them for only two months.

Animal and human studies have suggested that high levels of anticocaine antibodies in the blood can sequester and inactivate cocaine before it enters the brain, reducing feelings of euphoria from the drug without causing any psychoactive effects or harmful interactions.

Dr. Bridget A. Martell of Yale University School of Medicine, New Haven, and colleagues conducted a 24-week phase 2b trial of a vaccine designed to increase levels of cocaine antibodies in the blood.

In the study of 115 cocaine-dependent individuals, 58 were randomly assigned to receive five vaccinations of the active vaccine, while the other 57 received placebo injections over 12 weeks.

In both groups combined, 94 (82 percent) completed the trial and their urine was tested for metabolised cocaine three times per week for 24 weeks.

Of the 55 participants who completed five active vaccinations, 21 (38 percent) attained blood cocaine antibody levels of 43 micrograms per milliliter or higher.

And those who did were found to have significantly more cocaine-free urine samples between weeks nine and 16 of the study than individuals who did not attain those antibody levels or who received placebo injections (45 percent vs. 35 percent cocaine-free urine samples).

The proportion of participants who reduced their cocaine by half was also greater in the group with high antibody levels than in those with a low antibody level (53 percent vs. 23 percent).

In addition, adverse events associated with the vaccine were mild or moderate, with the most frequent being hardening and tenderness at the injection site.

No treatment-related serious adverse events, withdrawals or deaths occurred.

"Optimal treatment will likely require repeated booster vaccinations to maintain appropriate antibody levels. Furthermore, efforts will be needed to retain subjects during the initial series of injections since antibody levels increased slowly over the first three months when patients were immunized according to the protocol used in these studies," wrote the authors.

"Other treatments need to be used during this early treatment period to encourage abstinence.

"Thus, the goals for future vaccine development will be to increase the proportion of subjects who can attain the desired antibody levels and to extend these periods of abstinence through long- term maintenance of these adequate antibody levels," they concluded.

The study was published in the latest issue of Archives of General Psychiatry, one of the JAMA/Archives journals. (ANI)