Thienopyridine derivatives produce irreversible inhibition of the platelet adenosine diphosphate receptor, thereby attenuating platelet aggregation in response to adenosine diphosphate released from activated platelets.19–20 Aspirin and thienopyridines derivatives have complementary mechanisms of action, and the combination of these agents inhibits platelet aggregation to a greater extent than either agent alone.21Combined antiplatelet therapy with aspirin and a thienopyridine is superior to systemic anticoagulation therapy for prevention of complications after coronary stent insertion. Thus, subacute vessel closure, which occurred 2 to 14 days after stent placement, was reported in 3 to 5% of cases in the initial series, despite the use of an aggressive antithrombotic regimen that included aspirin, dipyridamole, dextran, and IV heparin overlapping with a vitamin K antagonist. The risk of acute complications is reduced with aspirin plus a thienopyridine.22–23 Thus, in a randomized trial24 that included 517 high-risk patients treated with Palmaz-Schatz stents (Cordis Corporation, Warren, NJ) for acute MI, suboptimal angioplasty, or other “high-risk” clinical and anatomic features, patients were assigned to antiplatelet therapy (aspirin plus ticlopidine) or anticoagulant therapy (aspirin, heparin, and a vitamin K antagonist) after successful stent placement. The primary end point, a composite of cardiovascular death, MI, CABG surgery, or repeat angioplasty, occurred in 1.5% of patients receiving antiplatelet therapy and 6.2% of those randomized to anticoagulant treatment (p = 0.01).24Subacute stent thrombosis occurred in 0.8% of patients in the antiplatelet therapy group and in 5.4% of those receiving anticoagulants. The Stent Anti-thrombotic Regimen Study25 randomized 1,653 lower-risk patients to aspirin alone (325 mg/d), the combination of aspirin (325 mg/d) plus ticlopidine (500 mg/d) for 1 month, or to aspirin (325 mg/d) plus warfarin after successful placement of a Palmaz-Schatz stent.25 The composite of death, target lesion revascularization, angiographic thrombosis, or MI at 30 days was reduced from 3.6% in patients assigned to aspirin alone and 2.7% in those assigned to aspirin plus warfarin to 0.5% in those receiving the combination of aspirin and ticlopidine (p < 0.001).25 Thus, based on these studies, the combination of aspirin plus a thienopyridine has become the standard of care.