antiplatelet

Antiplatelet refers to a class of drugs that inhibit platelet activation or aggregation to reduce arterial thrombus formation. They target platelets rather than the coagulation cascade and are used to prevent events such as myocardial infarction and ischemic stroke. They are distinct from anticoagulants, which inhibit clotting factors in the coagulation pathway.

Major antiplatelet agents include aspirin, P2Y12 receptor inhibitors (clopidogrel, prasugrel, ticagrelor), glycoprotein IIb/IIIa inhibitors (abciximab, eptifibatide, tirofiban), dipyridamole, and phosphodiesterase inhibitors such as cilostazol. Aspirin irreversibly inhibits cyclooxygenase-1, reducing thromboxane A2 and platelet aggregation; its antiplatelet effect lasts for the life of the platelet (about 7–10 days). Clopidogrel and prasugrel are prodrugs that irreversibly block the P2Y12 receptor after hepatic activation; ticagrelor is a reversible P2Y12 antagonist with a shorter half-life. GP IIb/IIIa inhibitors are intravenous agents that block the final common pathway of platelet aggregation and are mainly used in acute coronary syndromes and percutaneous coronary intervention. Dipyridamole and cilostazol inhibit platelet function through increasing intracellular cAMP but are used selectively for specific indications such as stroke prevention (dipyridamole-aspirin) or intermittent claudication.

Indications include secondary prevention of cardiovascular events, prevention of stent thrombosis after PCI, and management of acute coronary syndromes or ischemic stroke in selected patients. Bleeding is the principal risk; the risk varies by agent and combination therapy. Monitoring is largely clinical, with laboratory tests reserved for specific circumstances.