Patients carrying two copies of the CYP2A6*38 allele or one copy of the *38 allele in combination with one copy of the *1A allele may have increased metabolism of nicotine as compared to patients carrying any combination of the *2 or *4 alleles but decreased metabolism as compared to patients carrying two copies of the *46 allele or one copy of the *46 allele in combination with one copy of the *1A allele. 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.