Here, we describe the first pharmacogenetic analysis of smoking cessation in a large population of smokers derived from placebo-controlled clinical trials testing the efficacy of varenicline and bupropion. In addition to drug metabolizing and nicotinic receptor genes, we investigated the primary varenicline transporter (SLC22A2), additional genes in the chromosome 15q25 locus (IREB2, LOC123688, and PSMA4), and two serotonin receptors (HTR3A and HTR3B) whose expression in the gut may contribute to nausea while on varenicline treatment (Gershon, 2004). We also examined whether variation in these candidate genes is associated with time to relapse to smoking or to nausea while on treatment.
