Can resistance to aspirin be reversed after an additional dose?

Aspirin resistance or aspirin non-responsiveness is a recently described phenomenon which has been consistently associated with an increased risk of cardiovascular events. This study was designed to determine the effects of an additional dose of 100 mg of aspirin on platelet function and proportion of aspirin non-responders using the platelet function analyzer-100 (PFA-100), in a well characterized population of stable coronary heart disease patients already on long-term aspirin treatment. Platelet function was assessed using PFA-100 in 141 patients (64.8 ± 10.1 years, 87.9% men) on long-term aspirin treatment (100 mg/day) before and 1 h after "in site" oral aspirin administration (100 mg). Prevalence of aspirin non-responders using PFA-100 was 50.7% (95% confidence interval 42.4-59). One hour after 100 mg of oral aspirin, reassessment of aspirin effects showed a prevalence of non-responders using PFA of 35.0% (95% CI 27.3-43.2) (P < 0.001 vs. pre-dose proportion). Using the PFA-100 system, reassessment of platelet function following oral administration of daily aspirin dosage significantly reduces the number of stable coronary disease patients considered to be non-responders to such treatment.