Laboratory Research

Nicotine Metabolism

Nicotine Metabolism Variability and Nicotine Addiction
Karen Ahijevych, Ph.D., R.N.
College of Nursing
Ohio State University

This report, by Dr. Karen Ahijevych of Ohio State University explores the genetic role of nicotine addiction by studying the biochemical metabolism, or the chemical digestion, of nicotine in the body. The report raises questions as to whether some people are more inclined to smoke due to their race. Although there are many other behavioral factors that influence nicotine addiction, such as duration of inhalation and differences in swallowing of nicotine-laden saliva, the genetic role also seems to play a part in initiation of consuming nicotine delivery systems.

Nicotine metabolism is complex because of its numerous steps. Ultimately, nicotine is converted by the body into a substance called cotinine, which is known as the metaolite in the process of metabolism. Since nicotine has such a short half-life of about 2 hours, the research used cotinine as a marker of exposure in smokers, due to its stability as a marker, having a half-life of about 20 hours.

The implications of a faster nicotine metabolism is that once all the nicotine in the body is used up, the smoker craves more nicotine and the urge to smoke rises. Therefore, people with slower nicotine metabolisms will feel the urge to smoke less frequently than other people. Metabolisms also change, depending on chemical and behavioral changes. For example, daily activities such as eating increase nicotine metabolism. It is believed that this contributes to the pattern we see in smokers to have the urge to smoke after meals. Nicotine clearance can increase almost 42% approximately 1 hour after the beginning of the meal. This could be attributed to the increase in blood flow to and through the liver while consuming.

Several earlier studies indicated that male smokers have faster nicotine metabolisms than females, and thus have the urge to smoke more often. This report noted that higher levels of cotinine were observed in African-American smokers than Caucasian smokers. This must mean that nicotine clearance systems were faster in Caucasian smokers, and thus they felt the urge to smoke more frequently than African-American smokers. This explains the higher smoking rate found among Caucasians than in African-American smokers.