Aspirin and Antiplatelet Agent ResistanceImplications for Prevention of Secondary Stroke

Oral antiplatelet drugs, including aspirin, clopidogrel and extendedrelease dipyridamole, are widely prescribed for the secondary prevention of vascular events, including stroke. Despite the benefits of antiplatelet therapy, 10–20% of patients experience a recurrent vascular event while taking antiplatelet medication. This article discusses the concept of antiplatelet resistance in general, focusing on aspirin resistance in particular, as a poorly defined cause of recurrent vascular events. Factors such as the lack of a standardized method to diagnose aspirin resistance and a poor clinical correlation with laboratory assays make the treatment of aspirin nonresponders difficult. In addition, there are confounding conditions such as diabetes mellitus that can affect aspirin resistance and determine a different course of treatment for these patients. Other antiplatelet options may also have resistant subpopulations; thus, alternative strategies for the secondary stroke patient must be explored.