Current Antiplatelet Agents in Acute Coronary Syndrome.

Sir, A coronary syndrome (ACS) comprises of ST segment elevation myocardial infarction (STEMI), non-ST segment elevation myocardial infarction (NSTEMI) and unstable angina (UA). Dual antiplatelet therapy with aspirin (ASA) and clopidogrel (P2Y12 receptor inhibitor) reduces cardiovascular (CV) death, MI and stroke. However, 5-44% of studied patient population showed high platelet activity despite use of clopidogrel. Ticagrelor and prasugrel (new P2Y12 receptor inhibitors) have shown to reduce l eve l o f p la te le t activation as compared to clopidogrel. While clopidogrel and prasugrel are irreversible inhibitors of P2Y12 receptors on platelet surface, tecagrelor is reversible and non competitive antagonist and is not a prodrug as it is with clopidogrel and prasugrel. Therefore, the platelet inhibited by clopidogrel or prasugrel are affected for rest of their lifespan and platelet function returns to normal by 5-10 days after stoppage of these agents. Prasugrel is contraindicated in patients with previous stroke, transient ischaemic attack (TIA), age of 75 years or above and weight below 60 Kg. Ticagrelor is contraindicated in patients with history of intracranial haemorrhage and patients taking strong CYP3A4 inhibitors. TRITON-TIMI 38 (Trial to assess improvement in therapeutic outcomes by optimizing platelet inhibition with prasugrel-thrombolysis in myocardial infarction) compared prasugrel (60 mg loading dose, 10 mg maintenance dose) to clopidogrel (300 mg loading dose, 75 mg maintenance dose )in double blind randomised control trial. 13,604 (10074-UA/NSTEMI and 3534-STEMI) moderate to high risk ACS patients were enrolled and followed for a minimum of 6 months and maximum of 15 months.1 Current Antiplatelet Agents in Acute Coronary Syndrome