Effects of Nicotine Metabolic Rate on Cigarette Reinforcement.

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.

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 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=0.032). Blacks smoked fewer cigarettes (p=0.008) and took fewer total puffs (p=0.002) compared to Whites. Among Whites, fast metabolizers by NMR had a shorter time to first cigarette compared to slow (p=0.014). Among fast metabolizers, Whites had, compared to Blacks, shorter latency to first cigarette (p=0.003) and higher number of total puffs (p=0.014) and cigarettes smoked (p=0.014). 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 to slow metabolizers.