Vaccine 'can block cocaine'

A VACCINE for cocaine addiction may be tested for the first time on humans this summer, and trials for a vaccine for nicotine addiction could follow.

A US company, ImmuLogic Pharmaceuticals, based in Massachusetts, has developed both vaccines. Trials on laboratory rats have reduced the addictive potential of cocaine by as much as 50 per cent. Researchers believe that the vaccine, used in conjunction with support services, could eliminate addicts' craving for the drug.

Cocaine has an immediate and powerful effect on the brain because its very small molecules can easily penetrate the blood-brain barrier. The vaccine attaches an antibody to the cocaine molecule, making it too large to pass easily through the barrier.

Researchers forced rats to become addicted to cocaine and trained them to self-administer more of the drug by pulling on a lever. They then vaccinated some of the rats. Although a substantial amount of cocaine still reached the brain in some cases, the vaccinated rats eventually stopped pulling on the levers.

The researchers are also trying to ensure that the vaccine will not lead addicts to change to other drugs, will not have an effect on the central nervous system and will be able to go through the placenta to provide protection for a foetus.

But Dr Barbara Fox, a senior researcher at ImmuLogic, points out that the vaccine would need to be accompanied by counselling and psychological support in case addicts tried to overcome the effects of the antibodies - for example, by increasing their intake of cocaine.

Human trials could begin in June or July if the US Food and Drug Administration gives the go-ahead. About four million people in the US are addicted to cocaine, or its derivative crack cocaine, for which the vaccine could also be used. It could be available within five years if trials are successful.

Dr Fox and her team are also working on a nicotine vaccine, but it may be next year before human trials begin. Nicotine is regarded as the most addictive drug: 100,000 people in Britain die each year from smoking- related diseases.