Pharmacogenomics of Antiplatelet Response - I (PARes-I)

Inclusion Criteria:

• Participants from the GeneSTAR cohort
• Unaffected with no overt coronary artery disease or serious vascular event (stroke or peripheral vascular disease diagnosis
• Presence of an occult coronary artery disease phenotype as defined by coronary artery calcium scores about the MESA (Multiethnic Study of Atherosclerosis) 75th percentile for age sex, and race or ≥ 1 stenoses in any of the major coronary arteries or main branches of > 50%, or coronary plaque volumetric scores above our own 75th percentile, or any combination on cardiac computed tomographic angiography (performed recently as part of the GeneSTAR study and present for all persons being recruited)/
• Presence of occult cerebrovascular disease defined as presence of white matter hyperintensities (WMH) thought to represent ischemic small vessel cerebrovascular disease, and /or the presence of lacunes (old small strokes), or the presence of an Atherosclerosis Risk in Communities Study (ARIC) silent stroke score on a visual analogue scales of 4 or more (on a scale of 0-9).
• Women who are postmenopausal.
• Women who use a reliable contraceptive method; a reliable contraceptive method will be defined as personal history of tubal ligation, ongoing use of intra-uterine device, or ongoing use of oral contraceptive pills.

Exclusion Criteria:

• Presence of any CAD or stroke, transient ischemic attacks, peripheral arterial disease
• Persons taking aspirin, NSAIDS, or any anti-coagulants who are medically unable to stop them for a two week pre-trial
• A history of allergy to aspirin or clopidogrel
• Weight < 60kg
• Age < 45 and > 75 years of age
• A history of recent or any active bleeding
• Serious or current co-morbidity (AIDS, cancer)
• Pregnant women as determined by urine dipstick pregnancy test
• Any aneurysms on cranial magnetic resonance imaging/magnetic resonance angiography (obtained recently in the GeneSTAR participants)
• Blood pressure above >=159/95mmHg
• History of a gastric or duodenal ulcer, or significant gastrointestinal disease, like regional enteritis
• Mental incompetence to make a decision to participate (developmentally disabled, and persons with diagnosed psychiatric disorders-documented in primary care records).