Adding Cilostazol to Dual Antiplatelet Therapy Achieves Greater Platelet Inhibition than High Maintenance Dose Clopidogrel in Patients With Acute Myocardial Infarction

BACKGROUND: Optimal platelet inhibition is an important therapeutic adjunct in patients acute myocardial infarction (AMI) undergoing coronary stenting. Whether adjunctive cilostazol to dual antiplatelet therapy (triple antiplatelet therapy) can inhibit enhanced platelet reactivity in patients with AMI yet has not been determined. The aim of this study was to assess the degree of platelet inhibition by triple antiplatelet therapy in patients with AMI. METHODS AND RESULTS: Immediately after emergency room arrival, patients with AMI received clopidogrel (600-mg loading dose, followed by 75 mg daily) and aspirin (300-mg loading dose and 200 mg daily throughout the study period). After patients underwent coronary stenting (n=90), they were randomly assigned to 1 of 3 groups before discharge: standard group, clopidogrel of 75 mg daily (n=30); high maintenance dose (MD) group, clopidogrel of 150 mg daily (n=30); and triple group, adjunctive cilostazol of 100 mg twice daily to clopidogrel of 75 mg daily (n=30). Platelet reactivity was assessed at predischarge and 30-day follow-up by conventional aggregometry and the VerifyNow P2Y12 assay. Predischarge platelet reactivities were similar in the 3 groups. At 30-day follow-up, inhibition of maximal aggregation with 20 microM ADP stimuli was 6.0% in the standard group, 19.1% in the high-MD group, and 42.4% in the triple group (P<0.001), whereas inhibition of late aggregation with 20microM ADP stimuli was 10.8%, 38.1%, and 66.4%, respectively (P<0.001). Similar results were demonstrated when 5 microM ADP was used. Furthermore, percent changes of P2Y12 reaction unit were significantly different among regimens (10.6% in the standard group, 30.7% in the high-MD group, and 43.0% in the triple group; P<0.001). With respect to high-postclopidogrel platelet reactivity (prespecified as 20 microM ADP-induced maximal aggregation >50% of light transmission), fewer patients in the triple group (13.3%) met the criteria as compared with those in the standard (76.7%) and high-MD groups (56.7%) at 30-day follow-up (P<0.001). In the triple group, there were more potent and consistent platelet inhibitions by all parameters as compared with the high-MD group except for percent changes of P2Y12 reaction unit (P=0.071). CONCLUSIONS: Among patients with AMI undergoing coronary stenting, triple antiplatelet therapy results in a greater antiplatelet effect at 30 days as compared with a high-MD clopidogrel or standard dual antiplatelet therapy.