Effects of Nicotine Metabolic Rate on Cigarette Reinforcement. Issue 8 (14th November 2019) - Liakoni, Evangelia
Abstract: Introduction: The rate of nicotine metabolism, estimated by the nicotine metabolite ratio (NMR), is an important determinant of tobacco dependence. This study investigated the effect of NMR on smoking behavior due to nicotine reinforcement during ad libitum smoking. Aims and Methods: As part of a larger study, participants were stratified based on saliva NMR as fast and slow metabolizers. After smoking a cigarette and measuring nicotine blood concentrations, participants smoked as desired over a 90-minute period. Analysis included time to first cigarette, total number of cigarettes, total number of puffs, and weight of tobacco consumed. Results: Sixty-one (48%) participants were fast metabolizers and 66 (52%) slow metabolizers by NMR. No significant differences were found regarding the smoking topography variables by NMR. Normal metabolizers by genotype ( n = 79) had a shorter time to first cigarette than reduced metabolizers ( n = 39; p = .032). Blacks smoked fewer cigarettes ( p = .008) and took fewer total puffs ( p = .002) compared with Whites. Among Whites, fast metabolizers by NMR had a shorter time to first cigarette compared with slow metabolizers ( p = .014). Among fast metabolizers, Whites had, compared with Blacks, shorter latency to first cigarette ( p = .003) and higher number of total puffs ( p = .014) and cigarettes smoked ( p = .014). Baseline cigarettes per day and nicotine elimination half-life significantly predicted topography outcomes. Conclusions: Saliva NMR did not predict cigarette reinforcement during a relatively brief period of ad libitum smoking. Differences were seen by race, with White fast metabolizers by NMR having shorter time to first cigarettes compared with slow metabolizers. Implications: After a 90-minute period of nicotine abstinence, NMR was not significantly associated with smoking reinforcement. Slow and fast metabolizers had similar time to first cigarette, number of cigarettes smoked, total number of puffs, and tobacco consumed; however, within-race differences show that within Whites, fast metabolizers had a faster time to first cigarette than slow metabolizers.