Aspirin and clopidogrel +/- heparin or thrombolytic co-therapy is well established and effective treatment for unstable cardiac patients. However, the major complication was gastrointestinal bleeding (GIB) due to peptic ulcer. In the prevention of GIB, anti-ulcer drug either H2-receptor antagonist (H2RA) and proton pump inhibitor (PPI) were commonly prescribed. There has been no prospective controlled study to compare the efficacy of these two classes of anti-ulcer drugs.