A blood test may enable doctors to predict which smokers using the nicotine patch are likely to experience the least amount of cravings and have the highest probability of success in quitting cigarettes, according to the results of a study in the June issue of the Journal of Clinical Pharmacology and Therapeutics.

The blood test, which is a measure of the rate at which nicotine is metabolized, may eventually be performed non-invasively using saliva or urine samples. "The ultimate aim here is to distinguish smokers who are likely to benefit from a standard dose of nicotine patch from those who may need a higher dose patch or an alternative therapy in order to succeed in quitting," said lead researcher for the study, Caryn Lerman, associate director for cancer control and population science at the Abramson Cancer Centre of the University of Pennsylvania, and Director of the University of Pennsylvania Transdisciplinary Tobacco Use Research Centre.

When nicotine is metabolized - or broken down in the body - it turns to cotinine. Cotinine is then metabolized to 3-hydroxycotinine (3-HC) by an enzyme in the liver. This study measured the ratio of these two breakdown products of nicotine among 480 smokers. A high ratio meant rapid metabolism of nicotine, which was associated with higher amounts of craving and greater difficulty in quitting cigarettes using the nicotine patch.

The smokers who participated in the study quit smoking and started using either the patch or the nicotine nasal spray for eight weeks. Measurements of carbon monoxide levels in exhaled air identified those who were not smoking at the eight-week and six-month intervals following the quit date. Study participants also provided information on level of cravings for cigarettes one week after their quit date.

"Using the rate of nicotine metabolism, we were able to predict the level of cravings and the efficacy of the nicotine patch," said Lerman. "Similar results could not be obtained for the nicotine spray, most likely because the subjects were able to compensate for rapid metabolism of nicotine by using the spray more often," he added.

This study was funded by the National Cancer Institute, the National Institute on Drug Abuse, and the Pennsylvania State Tobacco Settlement. The Robert Wood Johnson Foundation has also supported the University of Pennsylvania's Transdisciplinary Tobacco Use Research Centre, which conducted this research.