The aim of this study is to demonstrate that the combination therapy of aspirin and clopidogrel napadisilate is not inferior to that of aspirin and clopidogrel bisulfate with respect to its effectiveness in inhibiting platelet aggregation, if it is given for four weeks to Coronary Artery Disease (CAD) patients who had been treated with a drug-eluting stent before > 12 months and had remained in a stable condition with a single antiplatelet agent, aspirin.

Inclusion Criteria:

• aged 20 to 80 years
• men and women with coronary artery disease who had been treated with drug-eluting stent placement before > 12 months
• patients who had remained in a stable condition with a single antiplatelet agent, aspirin
• patients who did not show any sign or symptom of the worsening of their angina within the last six months that required a coronary artery intervention, a coronary artery bypass, or coronary angiography

Exclusion Criteria:

• Patients who were taking another antiplatelet or anticoagulant drug such as clopidogrel, warfarin, or cilostazol in addition to aspirin, unless they could withdraw from such other drug/s, in which case they could be enrolled in the study after a two-week wash-out period
• Patients who were suffering from drug abuse or alcohol addiction
• hypersensitivity to clopidogrel or aspirin
• severe liver disease (ALT or AST ≥ 10 times the upper normal limit)
• active hemorrhage such as gastro-intestinal ulcer or intracranial hemorrhage
• a high risk of bleeding (blood coagulation disorder, uncontrolled severe hypertension, active bleeding, or history of severe bleeding)
• pregnant or lactating women
• women with childbearing potential who were not using an appropriate contraception method
• had medical or mental contra-indications to the study treatment