Mounting evidence suggests a crucial role for the loss-of-function CYP2C19*2 genetic variant. Carriers of CYP2C19*2 allele were at 30% higher risk for major adverse clinical events compared to non-carriers. CYP2C19*2 alone was also associated with increased mortality and stent thrombosis. These findings led the American Food and Drug Administration to issue a boxed warning for clopidogrel stating that poor metabolizers may not receive the full benefit of the drug. Thus, routine genotyping in the context of dual anti-platelet therapy is necessary.