Prasugrel 5mg Versus High Dose Clopidogrel in Clopidogrel Resistant Patients Aged ≥75 Years and/or Weighing <60 kg Post Percutaneous Coronary Intervention (PCI)

Inclusion Criteria: 1. Age ≥18 years old 2. Patients having PCI with stenting 24 hours prior randomization, meeting the following criteria : * Acute coronary syndrome (unstable angina or myocardial infarction) * TIMI risk score\>2 3. Platelet reactivity in PRU ≥235 24 hours post-PCI 4. Age≥75 years and/or weight\<60 Kg 4\. Informed consent obtained in writing Exclusion Criteria: * A history of bleeding diathesis * Chronic oral anticoagulation treatment * Contraindications to antiplatelet therapy * Known platelet function disorders * PCI or coronary artery bypass surgery \< 3 months * Unsuccessful PCI (residual stenosis \> 30% or flow \< Thrombolysis in myocardial infarction flow 3) * Planned staged PCI in the next 30 days * Hemodynamic instability * hemodialysis * Creatinine clearance \<25 ml/min * inability to give informed consent * High likelihood of being unavailable for the Day 30 * History of gastrointestinal bleeding, genitourinary bleeding or other site abnormal bleeding within the previous 6 months. * Other bleeding diathesis, or considered by investigator to be at high risk for bleeding on longterm antiplatelet therapy. * Any previous history of ischemic stroke, transient ischemic attack, intracranial hemorrhage or disease (neoplasm, arteriovenous malformation, aneurysm). * Thrombocytopenia (\<100.000 / μL) at randomization * Anaemia (Hct \<30%) at randomization * Polycythaemia (Hct \> 52%) at randomization * Periprocedural IIb/IIIa inhibitor administration