CYP2C19 and acute coronary syndrome: However, testing for loss-of-function variation in the gene CYP2C19 (part of the P450 family of enzymes) is now recommended for informing the use of the antiplatelet drug clopidogrel in individuals with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) [92] because such variants may adversely affect platelet activity and increase the risk of cardiovascular events.