Abstract: AIM:To investigate the influence of diuretics on the anti-platelet effect of clopidogrel in patients with acute coronary syndrome (ACS) after percutaneous coronary intervention (PCI). METHODS: Consecutive post-PCI ACS patients treated with clopidogrel in our hospital from September 2009 to September 2011 were recruited and followed-up for 1 year. General and clinical characteristics were compared between patients with and without cardiac endpoints by univariate analysis. Logistic regression, Kaplan-Meier curves and Cox regression were used to analyze the influence of diuretics on major adverse cardiac events (MACE, including cardiac death, nonfatal acute myocardial infarction or stroke and emergent coronary revascularization) or composite events (including MACE, definite or suspicious stent thrombosis, hospitalization for recurrent myocardial ischemia or unstable angina and non-emergent coronary revascularization) in patients treated with clopidogrel. RESULTS: A total of 750 consecutive post PCI ACS patients treated with clopidogrel were recruited, of whom 664 patients completed the 1-year follow-up. Univariate analysis showed that age and use of stains, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and diuretics were significantly different between patients with (n=164) and without (n=500) events (P<0.05, P<0.01). Logistic regression analysis indicated that use of diuretics was the independent risk factor for MACE (OR: 2.99, 95% CI: 1.37-6.54, P<0.01) and composite events (OR: 2.37, 95% CI: 1.53-3.68, P<0.01). Kaplan-Meier curves and Cox regression showed that the cumulative hazard of composite events was significantly higher in patients treated with diuretics than those without diuretics (P<0.01). CONCLUSION: Diuretics increases the risk for cardiac ischemic events in post-PCI ACS patients treated with clopidogrel.