Effect of cilostazol on optimized standard antiplatelet therapy in a patient with a cytochrome P450 2C19 *2/*2 genotype.

A 54-year-old man with acute coronary syndrome underwent primary percutaneous coronary intervention (PCI) to implant a bare metal stent. Three weeks later, a subclinical in-stent thrombus was found at staged PCI despite dual antiplatelet therapy with aspirin and clopidogrel. Platelet function tests revealed high post-treatment platelet reactivity, indicating an inadequate response to clopidogrel. The patient's cytochrome P450 2C19 genotype was *2/*2. Cilostazol at 200 mg/day was initiated in addition. Three months later, platelet inhibition was enhanced, and no thrombus was detectable by coronary angiography. Our experience suggests that triple antiplatelet therapy with cilostazol as well as aspirin and clopidogrel could prevent stent thrombosis with improved clopidogrel responsiveness.