It is unclear whether the concomitant use of omeprazole (PPI) with clopidogrel would result in a decrease in platelet function parameters through the CYP2C19 clopidogrel activation pathway. The specific aim of the proposed study is to determine whether the interaction between PPIs and clopidogrel is dependent on CYP2C19 haplotype. We hypothesize that among subjects with a LOF genotype, the interaction between clopidogrel and PPIs is greater than that in subjects with the wild type genotype7 and is manifest in both platelet function parameters and in conversion of clopidogrel to its active metabolite.