AIMS:The optimal antithrombotic regimen for non-ST elevation acute coronary syndrome(NSTEACS) has not yet been defined and the risk of ischemic events remains high in these patients. We aimed to evaluate the effect of cilostazol on agonist induced platelet aggregation and serum plasminogen activator inhibitor-1(PAI-1) in the patients with NSTEACS administered along with the standard antiplatelet regimen. PATIENTS AND METHODS:40 patients of NSTEACS presenting within 72 h of onset of symptoms were randomized to cilostazol or placebo in 1 : 1 ratio, in whom a conservative treatment strategy was adopted. Cilostazol 100 mg b.i.d was administered within 12 h of hospital admission for 7 days along with standard doses of aspirin and clopidogrel. The primary end points were effect on agonist-induced platelet aggregation and serum PAI-1 levels after 7 days of treatment. Safety and clinical outcome assessment were also done at 7 and 30 days. RESULTS:Patients in the triple therapy group showed significant decrease in the ADP (25.5 +/- 27.4 vs. 5.6 +/- 8.4; p = 0.003) and collagen (24.9 +/- 25.5 vs. 11.7 +/- 11; p = 0.04) induced percentage platelet aggregation after 7 days of treatment compared to the dual therapy group. There was no significant change in levels of serum PAI-1 (50.30 +/- 10.17 ng/ml vs. 53.47 +/- 14.08 ng/ml; p = 0.42). The composite of recurrent ischemia, myocardial infarction, need for intervention and death occurred in 4 patients in the cilostazol group compared to 7 in the placebo group at the end of 30 days of follow-up (p = 0.48). CONCLUSION:Cilostazol has additional platelet aggregation inhibition action in patients with NSTEACS along with aspirin and clopidogrel.