FRIDAY, May 23 (HealthDayNews) -- Although it has only been tested in rats and mice, a new nicotine vaccine shows promise in ending nicotine addiction and helping smokers kick the habit.

"We have created a new type of nicotine vaccine based on an analog of nicotine which allows the immune system to provide potent antibodies to effectively remove nicotine from the body before it reaches the brain," says lead researcher Kim D. Janda, a professor of chemistry from The Scripps Research Institute in La Jolla, Calif.

The vaccine could act as a crutch for people trying to stop smoking by preventing nicotine from reaching the brain, Janda says. "If one can effectively block nicotine from reaching the brain, there is a good chance of helping people kick the smoking habit."

Other nicotine vaccines have been tested but don't appear to work very well, including one previously developed by the Scripps' team, Janda notes.

About 12 years ago, Janda's team developed a successful cocaine vaccine, but when they first developed a nicotine vaccine, the researchers found it wasn't very effective.

Janda says the researchers didn't understand why the earlier nicotine vaccine was ineffective, since the nicotine and cocaine molecules are similar. When they went back and looked more closely, they found the cocaine molecule was restricted in its movement while the nicotine molecule wasn't.

"Unlike cocaine, nicotine is free to move and tumble around," Janda says. "So we made an analog of nicotine that can't move or tumble around and this was able to give us a much better vaccine," he adds.

The next step in the development of this new vaccine is to do toxicology studies. Once the researchers are sure the vaccine is safe, and they suspect it is, it will be ready for clinical trials.

Their report on the vaccine will appear in the June 18 issue of the Journal of the American Chemical Society.

Nicotine-replacement therapies, such as the patch or gum, aren't as effective as people had hoped they would be, Janda says. His team is looking for other ways to treat nicotine addiction.

The vaccine is designed to help smokers during the critical first 90 days of smoking cessation, when many relapse. The vaccine has been tested in two forms. The active form requires that people receive boosters, which would be effective for several months, while in its passive form people would be given the antibodies, which last for a few weeks, Janda notes.

Jed Rose, a professor of biological psychiatry and director of the Nicotine Research Program at Duke University, says the merits of this particular approach aren't yet clear. However, "as a general strategy, nicotine vaccines merit further investigation, and might ultimately have clinical application to tobacco addiction prevention or treatment."

David G. Gilbert, a professor of psychology at Southern Illinois University, adds that "one of the challenges of this approach is that smokers can easily increase the amount of nicotine that they obtain from a cigarette. Thus, smokers might be able to fully overcome the inhibitory effect of the vaccine by increasing their dose of nicotine."

He notes that it's possible that, "like [the] nicotine patch and gum and Zyban, the antidepressant medication used to help smokers quit, the vaccine might be helpful to some but not others who are attempting to quit smoking."

More information

To learn more about nicotine addiction, visit the National Institute on Drug Abuse or the U.S. Centers for Disease Control and Prevention.

Last Updated: May 23, 2003