CYP2C19 enzyme plays a role in the processing or metabolizing of at least 10% of commonly prescribed drugs, including a very used antiplatelet drug. CYP2C19 is involved in the metabolism of antidepressants and is also necessary to convert some drugs into their active form to function in the body. SNPs in this gene might cause several adverse events (cardiotoxicity, toxicity for the CNS, hepatotoxicity). The two most common CYP2C19 gene polymorphism associated with impaired drug metabolism are CYP2C19*2 and CYP2C19*3. CYP2C19*17 (-806 C>T) increases the enzyme’s ability to metabolize drugs (40% increase) such as the metabolism of Smephenytoin (anti-convulsant), omeprazole (proton pump inhibitor), and citalopram (antidepressant SSRI)

CYP2C19*2: 681 G>A (Prevalence ~15% among Caucasians)

CYP2C19*3: 636 G>A (Prevalence <1% in Caucasians)

CYP2C19*17: 806 C>T (Allele frequency ~18% in Caucasians)