Aspirin Resistance: An Evaluation of Current Evidence and Measurement Methods

Authors

  • Christopher P. Martin Pharm.D.,

    1. Division of Pharmacotherapy, College of Pharmacy, University of Texas at Austin, Austin, Texas
    2. Department of Pharmacology, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas.
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  • Robert L. Talbert Pharm.D., FCCP

    Corresponding author
    1. Division of Pharmacotherapy, College of Pharmacy, University of Texas at Austin, Austin, Texas
    2. Department of Pharmacology, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas.
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BCPS, Clinical Pharmacy Programs—MSC 6220, University of Texas Health Sciences Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229–3900.

Abstract

Aspirin resistance is a poorly characterized phenomenon, whereby certain patients do not benefit antithrombotic effect of aspirin. The frequency of aspirin resistance is unknown, but estimates range from 5–60%. The mechanism of aspirin resistance also is unknown; proposed mechanisms are poor patient compliance, poor aspirin absorption, increased isoprostane activity, platelet hypersensitivity to agonists, increased cyclooxygenase-2 activity, a cyclooxygenase-1 polymorphism, and the platelet alloantigen 2 polymorphism of platelet glycoprotein IIIa. Aspirin resistance appears to be dose related in some patients and therefore may be overcome with high doses. Evidence indicates that aspirin resistance is a dynamic state, with significant intrapatient variability in aspirin sensitivity with time. To date, a sensitive and specific assay of aspirin effect that reliably predicts treatment failure has not emerged. However, several commercially available products are being marketed for this purpose without convincing clinical data. Despite a wealth of literature on the topic, aspirin resistance remains an enigma. Further investigation is needed regarding strategies to identify and treat patients resistant to aspirin.

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