AspirinSensitivity and SpecificityAnti-Inflammatory Agents, Non-SteroidalPlatelet Aggregation InhibitorsCyclooxygenase InhibitorsIbuprofenThromboxane B2Cyclooxygenase 2 InhibitorsTiclopidineNaproxenDiclofenacSalicylatesPlatelet AggregationDrug Therapy, CombinationDose-Response Relationship, DrugTime FactorsPlatelet Function TestsContrast SensitivityGastrointestinal DiseasesGastrointestinal HemorrhageStomach UlcerCyclooxygenase 1Prostaglandin-Endoperoxide SynthasesProspective StudiesAcetaminophenRisk FactorsBlood PlateletsReproducibility of ResultsCyclooxygenase 2Drug ResistanceSodium SalicylatePeptic UlcerPeptic Ulcer Hemorrhage