Impact of CYP2C19 Genotype-guided Approach in Antiplatelet Therapy on Platelet Reactivity Index Among Coronary Artery Disease (CAD) Patients

A panel of genes including CYP2C19\*2 (rs4244285) and CYP2C19\*3 (rs4986893) will be genotyped using the real-time PCR and the expected turnover time will be 48 hours. Patients who are identified to have reduced function CYP2C19 allele will receive 90 mg ticagrelor and patients with wild-type CYP2C19 allele will receive clopidogrel 75 mg in the next scheduled dose. The switching done from clopidogrel to ticagrelor is supported by Antiplatelet Therapy Switching Clinician Guideline, whereby in the maintenance or low risk phase, there is generally no need to administer a loading dose of ticagrelor; one can switch directly to ticagrelor maintenance dose 24 hours after the last dose of clopidogrel