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drug interaction(s) of warfarin with antiplatelet agents

Indications: - aspirin & clopidogrel are recommended for patients after acute myocardial infarction (MI), & many patients with acute MI also have indications for warfarin - patients with atrial fibrillation* - prophylaxis for venous thromboembolism * addition of aspirin to warfarin may not reduce risk of myocardial infarction in patients with stable coronary artery disease [3] - no data after cororary revascularization Drug interactions: - combination of warfarin plus antiplatelet agent associated with substantial risk of serious bleeding - adjusted relative risks for fatal & nonfatal bleeding relative to aspirin alone: a) 1.23 for warfarin alone b) 1.33 for clopidogrel alone c) 1.47 for aspirin plus clopidogrel d) 1.84 for aspirin plus warfarin - ref [3] gives a much higher relative risk (7.3) e) 3.52 for clopidogrel plus a vitamin K antagonist f) 4.05 for aspirin plus clopidogrel plus warfarin - adjusted number needed to harm is 12.5 (aspirin plus clopidogrel plus warfarin) [2]

Properties

DRUGS: warfarin antiplatelet agent

References

  1. Rogacka R et al, Dual antiplatelet therapy after percutaneous coronary intervention with stent implantation in patients taking chronic oral anticoagulation. J Am Coll Cardiol Intv 2008, 1:56 PMID: 19393145 - Johnson SG et al, Outcomes associaed with combined antiplatelet and anticoagulant therapy. Chest 2008, 133:948 PMID: 18198244
  2. Sorensen R et al. Risk of bleeding in patients with acute myocardial infarction treated with different combinations of aspirin, clopidogrel, and vitamin K antagonists in Denmark: A retrospective analysis of nationwide registry data. Lancet 2009 Dec 12; 374:1967. PMID: 20006130
  3. Hamon M et al. Incidence, source, determinants, and prognostic impact of major bleeding in outpatients with stable coronary artery disease. J Am Coll Cardiol 2014 Oct 7; 64:1430. PMID: 25277612 - Dauerman HL. Reconsidering the necessity of aspirin in stable coronary artery disease. J Am Coll Cardiol 2014 Oct 7; 64:1437 PMID: 25277613