CYP2C19 enzyme plays a role in the processing or metabolizing of at least 10% of commonly prescribed drugs, including clopidogrel, an antiplatelet drug. CYP2C19 enzyme converts clopidogrel (an inactive prodrug) to its active form, which is necessary for the drug to function in the body. CYP2C19 is also involved in the metabolism of antidepressant such as amiptriptyline, moclobemide, citalopram and escitalopram. SNPs in this gene might cause several adverse events (cardiotoxicity, toxicity for the CNS, hepatotoxicity) The two most common CYP2C19 gene polymorphism associated with clopidogrel resistance are CYP2C19*2 and CYP2C19*3 , which result in the production of a nonfunctional (=loss of function) CYP2C19 enzyme that is unable to activate clopidogrel.

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

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

The SNP CYP2C19*17 806 C>T (allele frequency ~18% in Caucasians) is in development at LaCAR. This SNP 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)