New Vaccine For Cocaine Dependence Shows Some Success

By Margarita Nahapetyan

Scientists from the United States who have completed early trials on an experimental vaccine for cocaine dependence have announced recently that the vaccine has shown some success in decreasing use in cocaine addicts and even helped some users kick the habit.

Similar to a standard vaccine, the cocaine vaccine makes the body produce antibodies to cocaine. When a person inhales, smokes, chews or injects cocaine and it enters the bloodstream, the antibodies absorb some of it before it can reach up the brain and the user gets an addictive and euphoric high. After that, while cocaine is trapped in the blood, an enzyme called cholinesterase finishes the job by degrading the chemical. In short, the theory is that high levels of anti-cocaine antibodies can inactivate cocaine before it gets to the brain, preventing addicts from getting high and ultimately break their dependency.

In the new study, researchers at Yale School of Medicine have tested a new experimental cocaine vaccine on 115 cocaine-dependent individuals who were also using heroin and were enrolled in a methadone-treatment program. The length of the study was a full three months. All the participants were randomly assigned into 2 groups - half of them were administered 5 injections of the vaccine in phases, allowing antibodies to build up, while the other half were in a control group and received just a placebo.

The investigators found that the vaccine produced a significantly higher levels of anti-cocaine antibodies in thirty eight per cent of the 55 patients who received all five doses of the vaccine. When antibody levels were highest - during weeks nine through 16 of the study period - there was a marked reduction in the cocaine use in these participants (as measured by urine samples taken 3 times a week). Overall, cocaine use was reduced by at least half in 53 per cent of the volunteers who produced a strong antibody response, when compared to 23 per cent of those who demonstrated a weaker antibody response.

Nearly 25 per cent of the study subjects did not produce cocaine antibodies after being vaccinated. In about 50 per cent of these cases, the experts assume smoking crack could be the major problem. Crack causes intensely hot cocaine molecules to attach to lung cells. The user's body starts producing antibodies against this damaged tissue, but as a result, rather than deciding that it is alien, the body thinks that the cell clusters are "self" and does not do anything to fight them.

Thomas Kosten, a psychiatrist at Baylor College of Medicine, who is a principal author of the study, said that the cocaine vaccine was only the start of a search for a fully effective treatment. The expert pointed out that 20 per cent of the participants who had been administered the vaccine failed to develop many anti-cocaine antibodies. Researchers also said that the vaccine blocked the euphoric effects of the cocaine, but it did not take away cravings for it. The conclusion is that the vaccine may not be suitable for cocaine users in the throes of an addiction and would only work for those who had made a strong decision to quit the habit.

The findings are published in the October 5 issue of the Archives of General Psychiatry.