Antiplatelet and antithrombin therapy for early management of acute coronary syndromes

Acute coronary syndromes (ACS) are defined as either unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), or ST-segment elevation myocardial infarction (STEMI). Their management is continuously evolving in terms of pharmacologic therapy. The usual cause of ACS is the disruption of an atherosclerotic plaque leading to formation of a thrombus within a coronary artery. Initial antiplatelet and antithrombin therapy for patients with ST-segment elevation (STE) ACS includes aspirin and unfractionated heparin (UFH). Patients presenting to the hospital early may undergo percutaneous intervention (PCI) with administration of additional medications such as clopidogrel and abciximab or may receive a fibrinolytic agent. Patients with non-ST-segment elevation (NSTE) ACS receive aspirin, clopidogrel, either a low-molecular-weight heparin or UFH, and, in selected patients, a glycoprotein (GP) IIb/IIIa receptor blocker. All of these agents have shown benefit when administered to patients with ACS, but results vary depending on the type of syndrome, timing of administration, and patient's overall risk. Their mechanism of action, role in ACS, clinical practice recommendations, adverse effects, and monitoring are reviewed. Some inherent limitations to agents such as aspirin and UFH require the need for newer treatment approaches. Therefore, newer classes of drugs such as the direct thrombin inhibitor bivalirudin and the selective factor Xa inhibitor fondaparinux are being explored as alternatives to heparins for ACS management.