Genotypic and Phenotypic Correlates of Resistance to Aspirin

Inclusion Criteria: * Volunteers 40 to 80 years old willing to sign consent and take 81 mg of aspirin for 7 - 10 days and return for laboratory testing. Exclusion Criteria: * Patient requiring more than 81 mg aspirin daily * Known GI bleeding attributed to ASA * Active peptic ulcer disease or history within the last year * Known aspirin allergy * Current use of: * warfarin, * heparin, * NSAIDs (except aspirin), * clopidogrel, * dipyridamole, * fish-oil/omega 3 supplements, * Women of childbearing potential who are pregnant, planning to become pregnant or nursing.