Subjects with the LOF allele will be selected along with age and gender-matched wild type controls and baseline platelet function studies will be performed (n=16 for each group). Subjects in each stratum will then be randomly assigned to receive one week of clopidogrel in combination with omeprazole or clopidogrel alone. Subjects initially assigned to clopidogrel + omeprazole will then take clopidogrel only and subjects initially assigned to clopidogrel only will take both clopidogrel and omeprazole.