Patients with one copy of the CYP2A6*1A allele in combination with one copy of the *4 or *9A allele may have increased metabolism of nicotine as compared to patients with one copy of the *4A allele in combination with the *9A allele, or patients with two copies of the *9A allele. Patients with two copies of the *1A allele may have increased metabolism of nicotine as compared to patients with one copy of the *1A allele in combination with one copy of the *2, *4A, *7, *9A, *10, *11 *12, *13, *15, *17, *19, *20, *23, *24A, *25, *26, *27, *28A or *35 alleles or or patients with two copies of the *4A, *7, *9A, *10, *11 *12, *13, *15, *17, *19, *20, *24A, *27, *28A or *35 alleles or patients with the *4A/*7, *4A/*9 *4A/*17, *9/*12 *9/*26 or *17/*20 diplotypes but may have decreased metabolism as compared to patients with two copies of the *46 allele or one copy of the *1A allele in combination with the *46 or *1x2 alleles. However, conflicting evidence has been reported for *24A. This annotation only covers the pharmacokinetic relationship between CYP2A6 and nicotine and does not include evidence about clinical outcomes. Other genetic and clinical factors may also affect nicotine metabolism.