Benefits and limitations of current antiplatelet therapies.

PURPOSE: The benefits and limitations of current antiplatelet therapies in the management of patients experiencing acute coronary syndrome (ACS) are reviewed.

SUMMARY: Antiplatelet agents, including aspirin, thienopyridines, and platelet glycoprotein (GP) IIb/IIIa receptor inhibitors, have become the foundation of antithrombotic therapy in the management of patients experiencing ACS. Despite aspirin's ability to reduce the risk for adverse thrombotic events in a broad range of patients, it has variable antiplatelet activity in individual patients. The term "aspirin resistance" describes the inability of aspirin to produce an anticipated effect on one or more tests of platelet function. Because a substantial proportion of patients are "resistant" to the antiplatelet effects of aspirin, and other pathways for platelet aggregation are not inhibited by aspirin, current guidelines recommend a dual antiplatelet regimen with a thienopyridine or GP IIb/IIIa inhibitor in addition to aspirin for patients with ACS, including patients undergoing percutaneous coronary intervention and stent placement. These guidelines are based on observational and randomized clinical trials supporting the effectiveness of dual antiplatelet therapy in reducing mortality, nonfatal myocardial infarction, and the need for urgent revascularization compared with placebo, aspirin therapy alone, or an anticoagulant regimen. Studies in small numbers of patients have also revealed that some patients may be resistant to a thienopyridine, with some suggestion of a genetic etiology. Additional studies are needed to provide more definitive answers.

CONCLUSION: Improved awareness by healthcare professionals of the benefits and limitations of various antiplatelet therapies should aid in the development of strategies to ensure patient compliance and thereby reduce the morbidity and mortality associated with premature discontinuation of dual antiplatelet therapy.