Low-dose aspirin increases aspirin resistance in patients with coronary artery disease

• Published in: The American journal of medicine Vol. 118; no. 7; p. 723
• Main Authors: Lee, Pui-Yin, Chen, Wai-Hong, Ng, William, Cheng, Xi, Kwok, Jeanette Yat-Yin, Tse, Hung-Fat, Lau, Chu-Pak
• Format: Journal Article
• Language: English
• Published: United States 01-07-2005
• Subjects: Aged; Aspirin - administration & dosage; Aspirin - therapeutic use; Coronary Disease - blood; Coronary Disease - drug therapy; Dose-Response Relationship, Drug; Drug Resistance; Female; Hemoglobins - metabolism; Humans; Male; Middle Aged; Platelet Aggregation - drug effects; Platelet Aggregation Inhibitors - administration & dosage; Platelet Aggregation Inhibitors - therapeutic use; Retrospective Studies
• ISSN: 0002-9343
• DOI: 10.1016/j.amjmed.2005.03.041

We sought to investigate the association of aspirin dose and aspirin resistance in stable coronary artery disease patients measured by a point-of-care assay.
We studied 468 consecutive stable coronary artery disease patients in a referral cardiac center who were taking aspirin 80 to 325 mg daily for > or =4 weeks. The VerifyNow Aspirin (Ultegra RPFA-ASA, Accumetrics Inc, San Diego, Calif) was used to determine aspirin responsiveness. An aspirin reaction unit (ARU) > or =550 indicates the absence of aspirin-induced platelet dysfunction, based on correlation with epinephrine-induced light transmission aggregometry. Demographic and clinical data were collected to analyze the predictors of aspirin resistance.
Aspirin resistance was noted in 128 (27.4%) patients. Univariate predictors of aspirin resistance include elderly (P = 0.002), women (P <0.001), anemia (P <0.001), renal insufficiency (P = 0.009) and aspirin dose < or =100 mg (P = 0.004). Multivariate analysis revealed hemoglobin (odds ratio [OR] 0.6; 95% confidence interval [CI] 0.51 to 0.69; P <0.001) and aspirin dose < or =100 mg (OR 2.23; 95% CI 1.12 to 4.44; P = 0.022) to be independent predictors of aspirin resistance. Daily aspirin dose < or = 100 mg was associated with increased prevalence of aspirin resistance compared with 150 mg and 300 mg daily (30.2% vs 16.7% vs 0%, P = 0.0062).
A 100 mg or less daily dose of aspirin, which may have lower side effects, is associated with a higher incidence of aspirin resistance in patients with coronary artery disease. Prospective randomized studies are warranted to elucidate the optimal aspirin dosage for preventing ischemic complications of atherothrombotic disease.