measures of deuterated (D2)-cotinine/(D2-cotinine + D2-nicotine) following oral administration in 189 European Americans demonstrated that CYP2A6*12 is a loss-of-function allele indistinguishable from CYP2A6*4 and CYP2A6*2 alleles, and that the CYP2A6*1B 5′ untranslated region conversion has a negligible impact on metabolism (19). After controlling for the CYP2A6 genotype, the authors found modest associations between increased metabolism and both gender and current smoking (19).
