Testing of cocaine vaccine shows it does not fully blunt cravings for the drug
Tuesday, January 5, 2010
Scientists may have created a vaccine against cocaine addiction: a series of shots that changes the body's chemistry so that the drug can't enter the brain and provide a high.
The vaccine, called TA-CD, shows promise but could also be dangerous; some of the addicts participating in a study of the vaccine started doing massive amounts of cocaine in hopes of overcoming its effects, according to Thomas R. Kosten, the lead researcher on the study, which was published in the Archives of General Psychiatry in October.
"After the vaccine, doing cocaine was a very disappointing experience for them," said Kosten, a professor of psychiatry and neuroscience at Baylor College of Medicine in Houston.
Nobody overdosed, but some of them had 10 times more cocaine coursing through their systems than researchers had encountered before, according to Kosten. He said some of the addicts reported to researchers that they had gone broke buying cocaine from multiple drug dealers, hoping to find a variety that would get them high.
Of the 115 addicts in the study, 58 were given the vaccine, administered in a series of five shots over 12 weeks, while 57 received placebo injections. Six people dropped out before the end of the study. The researchers recruited the participants from a methadone-treatment program in West Haven, Conn., which made it possible to track them for the full 24 weeks of the study. The patients were addicted to cocaine and heroin; TA-CD is designed to work only on cocaine, including the crack form of the drug.
Like disease vaccines, TA-CD stimulates a person's immune system to produce antibodies. Of those who received all five vaccine injections, 38 percent reached antibody levels that were high enough to dull the effects of the drug. The antibodies stayed active for eight to 10 weeks after the last shot.
In the high-antibodies group, 53 percent stayed off cocaine more than half the time once they had built up immunity. That compares with 23 percent of those who produced fewer antibodies. The researchers monitored cocaine use through regular urinalysis.
"In this study, immunization did not achieve complete abstinence from cocaine use," Kosten said. "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."
About a quarter of those who received the vaccine did not make sufficient antibodies at all; Kosten isn't sure why.
"That's the million-dollar question," said Margaret Haney, a professor of clinical neuroscience at Columbia University Medical Center, who is also researching the cocaine vaccine though she was not involved in Kosten's study.
In October, the journal Biological Psychiatry published online an article by Haney that also tested the effects of TA-CD.
Through newspaper ads, Haney had recruited 15 cocaine-dependent men to participate in her study. (Only 10 stayed to the end.)