To compare the effect of increased dosing of clopidogrel and adding cilostazol to standard dose of clopidogrel after the insertion of drug-eluting stent in patients with clopidogrel resistance

Using dual antiplatelet agents with aspirin and clopidogrel is essential after drug-eluting stent implantation to prevent restenosis and stent thrombosis. However, variable platelet response and potential resistance to therapy have emerged with clopidogrel. Several studies showed that clopidogrel resistance is associated with increased cardiovascular events after coronary interventions. New antiplatelet therapeutic strategy of is needed in case of clopidogrel resistance. We started this study to compare the effect of double dosing of clopidogrel to 150mg per day and adding cilostazol to standard dose of clopidogrel after the insertion of drug-eluting stent in patients with clopidogrel resistance.

Inclusion Criteria:

• Patient with clopidogrel resistance with treatment of dual antiplatelet agent, aspirin and clopidogrel, for more than 4 weeks after drug-eluting stent
• Clopidogrel resistance is defined as a patients with platelet inhibition less than 30% in platelet function test(VerifyNow-P2Y12 assayTM, Accumetrics, San Diego, CA, USA)

Exclusion Criteria:

• Acute myocardial infarction within 2 weeks
• Unstable angina within 2 weeks
• History of using glycoprotein IIb/IIIa inhibitor within 1 month
• Cerebral infarction within 3 months
• Bleeding diathesis like coagulation disorder, thrombocytopenia (platelet count < 100,000/uL)
• history of gastrointestinal bleeding or genitourinary bleeding within 3 months
• needed oral anticoagulation
• aspirin, clopidogrel or cilostazol hypersensitivity
• congestive heart failure
• serum creatinine level >2mg/dl
• malignancy
• using cytochrome P450 inhibitor (eg, itraconazole)