If you are one of the 5.8 million Canadians who smoke, and you want to quit, keep an eye on your metabolism. \n\nA study conducted by researchers of the Centre for Addiction and Mental Health, the University of Toronto and the University of Pennsylvania finds that the way your body metabolizes can help determine the chance of quitting successfully. It also helps to target the type of treatment you should follow.\n\nQuitting isn't easy. Nearly 70% of those who try to do so relapse within a week. Until now, it was thought that some smokers might have a better or worse genetic disposition to quit. But that did not help identify the best treatment — nicotine patches or prescription pills. But success in quitting, it now appears, has more to do with how quickly the smoker breaks down nicotine.\n\nResearchers found that "normal" metabolizers will be more successful if they use a prescription pill, such as varenicline, rather than the ubiquitous nicotine patch. In this group, 40% of the "normal" metabolizers who used varenicline still abstained from smoking at the end of the treatment, compared with 22% of the "normal" group who used a nicotine patch. \n\nOn the other hand, slow metabolizers find it easier to quit and are better off using the patch. In the tests, varenicline was just as effective for them as a patch, but led to more negative side effects. \n\nThe difficulty for "normal" metabolizers is that the level of nicotine in their body drops more quickly, causing them to experience cravings, and thus to relapse. Varenicline is a better "crutch" for them in that it increases their level of dopamine, the "feel-good" hormone, thereby reducing cravings.