In our study, we observed an association between CYP2B6 polymorphisms and response to bupropion treatment. CYP2B6 is the primary metabolizing enzyme for bupropion (as well as a secondary enzyme for nicotine metabolism) thus the effectiveness of bupropion treatment in smoking cessation may be determined by the rate of its metabolism, as indicated by the CYP2B6 genotype. This is consistent with previous studies, in which CYP2B6 polymorphisms have been shown to affect the pharmacokinetics of bupropion (Kirchheiner et al, 2003) and the likelihood of achieving abstinence with bupropion in smoking cessation trials (Lee et al, 2007). However, the polymorphisms associated with response to bupropion in our study differed from those identified in previous studies (which were not successfully genotyped in our study), thus this does not represent a true replication. A better understanding of these associations may come from the identification and characterization of additional functional alleles affecting CYP2B6 activity or expression.
