Abstract 3889: Antecedent Aspirin Dose and Platelet Inhibition with Clopidogrel in Patients After Coronary Stenting and Ischemic Stroke: Analysis of 711 cases of Dual Antiplatelet Therapy
Background: Numerous randomized data suggest that combination of clopidogrel (C) with aspirin (ASA) yielded better clinical outcomes than monotherapy. However, the impact of ASA dose on the antiplatelet efficacy of clopidogrel is unclear, but may be important for the maintenance of the delicate balance between sustained vascular protection and increased bleeding risks. We sought to compare the antiplatelet profile of ASA 81mg (n=252) versus ASA 325mg (n=459) before and during conventional C loading (300mg) and maintenance (75mg/daily) doses.
Methods: Secondary post-hoc analyses of an existing dataset consisting of 711 patients after coronary stenting (n=601), and post-ischemic stroke (n=110) treated initially with ASA for at least 1 month, and then with C+ASA for at least 7 days. Platelet biomarkers include conventional, and the whole blood aggregometry, rapid cartridge-based analyzers, and expression of PECAM-1, P-selectin, and GPIIb/IIIa by flow cytometry.
Results: At baseline (before clopidogrel) there was a consistent trend towards more potent platelet inhibition with ASA 325 mg when compared with ASA 81 mg for every platelet-activation measure except for PECAM-1 expression. However, after a week of C+ASA, the platelet biomarkers became very similar between ASA 81 mg and ASA 325 mg, and identical for collagen-induced aggregation, PFA-100 Analyzer readings, and P-selectin expression.
Conclusions: Before addition of C, ASA 325 mg trended to provide stronger platelet inhibition than ASA 81mg. However, when C+ASA are used in combination, higher ASA dose does not yield superior antiplatelet benefit. Given that the existing body of evidence supports the comparable efficacy and superior safety of lower doses of aspirin vs. higher doses, unless future randomized data suggest otherwise, ASA 81 mg should be used in combination with clopidogrel. These data strongly support reduced aspirin dose recommended by the recent AHA/ACC guidelines update.