A 4 week-duration cross-over study on Ticagrelor and Clopidogrel for the Acute Coronary Syndrome (ACS) and Chronic Kidney Disease (CKD) subjects, focusing on the platelet inhibition and safety observation.

Acute coronary syndrome is a high mortality and costly disease. Antiplatelet therapies, including aspirin and P2Y12 antagonist, play important roles at the acute and subacute stage treatment for acute coronary syndrome, especially after coronary stent implantation. Patients with decreased estimated glomerular filtration rate (eGFR) experience higher cardiovascular morbidity and mortality. Clopidogrel, one of P2Y12 receptor antagonists, inhibits the receptor's activation by blocking its interaction with ADP. However, the efficacy of clopidogrel shows substantial variation and residual platelet reactivity, which is related to adverse cardiovascular outcome, especially in impaired renal function. Our study aims to check the platelet inhibition rate comparing both medication with a cross-over study among CKD subjects and ACS condition.

Inclusion Criteria:

1. Provision of informed consent prior to any study specific procedures
2. Female and male, age between 20-75 years
3. Stage 3-5 chronic kidney disease (eGFR<60ml/min) patients or ESRD
4. Taking standard treatment dose of clopidogrel (75mg/day) for more than 1 week
5. Patients were eligible for enrollment if they were hospitalized for an acute coronary syndrome, with or without ST-segment elevation, with an onset of symptoms during the past 6 months.
6. For patients who had an acute coronary syndrome without ST-segment elevation, at least two of the following three criteria had to be met: ST-segment changes on electrocardiography, indicating ischemia; a positive test of a biomarker, indicating myocardial necrosis; or one of several risk factors (age ≥60 years; previous myocardial infarction or coronary-artery bypass grafting [CABG]; coronary artery disease with stenosis of ≥50% in at least two vessels; previous ischemic stroke, transient ischemic attack, carotid stenosis of at least 50%, or cerebral revascularization; diabetes mellitus; peripheral arterial disease).
7. For patients who had an acute coronary syndrome with ST-segment elevation, the following two inclusion criteria had to be met: persistent ST-segment elevation of at least 0.1 mV in at least two contiguous leads or a new left bundle-branch block.

Exclusion Criteria:

1. Oral anticoagulation therapy that cannot be stopped
2. Increased risk of bradycardia
3. Concomitant use of strong CYP3A inhibitor/inducers
4. Unwilling to sign inform consent
5. Allergic or contraindicated to any study medications