The strong genotype/ phenotype correlation reported here led us to examine other validated probes of CYP2A6 activity, namely D2-trans-3′-hydroxycotinine : D2-cotinine following oral nicotine administration [14]and D0-trans-3′-hydroxycotinine : D0-cotinine during ad libitum smoking[13]. The trans-3′-hydroxycotinine: cotinine ratio was previously found significantly correlated with nicotine clearance 240 minutes following oral deuterated-nicotine administration [14]. Using the same variables as previously, the multivariate model predicts log(D2-trans-3′-hydroxycotinine : D2-cotinine) at 240 minutes with an R2 = 0.438. The ratio of D0-trans-3′-hydroxycotinine : D0-cotinine was determined in current smokers(table 2). In this sample, a multivariate model predicts log(D0-trans-3′-hydroxycotinine : D0-cotinine) with an R2 = 0.476.
