The CYP2B6 enzyme is the primary enzyme involved in the metabolism of the bupropion (Faucette et al. 2000) and the CYP2B6*5 and *6 variants are associated with slower bupropion metabolism (Hesse et al. 2004; Lang et al. 2001; Loboz et al. 2006). CYP2B6 genotype was examined as a predictor of relapse in a placebo-controlled trial of bupropion for smoking cessation (Lerman et al. 2002). 426 participants of European ancestry were genotyped for the functional C1459T (CYP2B6*5) variant and received bupropion or placebo for 10 weeks. Female smokers carrying the decreased activity allele reported greater increases in cravings following the target quit date and had higher relapse rates on placebo, which were reversed with bupropion (Lerman et al. 2002). David and others examined a sample of 291 smokers of European ancestry who participated in a double-blind randomized 12-week trial of bupropion versus placebo. Individuals who carried both the CYP2B6*5 allele and the dopamine D2 receptor DRD2-Taq1A allele demonstrated the highest long-term abstinence rates with bupropion (David et al. 2007).
