In a number of studies, variation in nicotine metabolism and CYP2A6 genotype have been associated with variation in smoking phenotypes [13, 16]. Polymorphisms are common in nicotine metabolism genes, although only a minority of the known variants have been fully characterized [17]. Recent studies have provided strong evidence for an association between cigarette consumption and CYP2A6 genotype in multiple populations[6, 16, 18]. Several polymorphisms in CYP2A6 are associated with lower smoking intensity; these include CYP2A6 *4, CYP2A6*2, an inactivation point mutation, CYP2A6*9, which alters the TATA box promoter region, and CYP2A6*12, a hybrid CYP2A6/CYP2A7 allele [19].
