Background: Variations in drug response may lead to treatment failure and/or adverse effects on individuals and subpopulations. Genetic factors have the greatest influence as the cause of this variation. The enzyme cytochrome P450 2A6 (CYP2A6) is an enzyme involved in xenobiotics metabolism phase in liver cells. CYP2A6 plays a role in the metabolism of coumarin, nicotine, and nitrosamine. In vi…