Faster nicotine clearance in women than in men has been reported previously [46–48] and our results support a modest contribution of gender to variation in nicotine metabolism. The effect of current smoking on nicotine metabolism is more controversial, with published evidence supporting both inductive [49, 50] and inhibitory effects[51]. We find an association between current smoking and faster metabolism of nicotine to cotinine (p=0.02 adjusting for CYP2A6 genotype), suggesting a slight induction of CYP2A6. Our study is the first to address this question in a relatively large sample, controlling for CYP2A6 genotype.
