Antiplatelet agents are medicines that reduce the ability of platelets to stick together and inhibit the formation of blood clots. Antiplatelet agents play a major role in the treatment and prevention of myocardial infarction (heart attacks), stent thrombosis, and ischemic stroke. Antiplatelet agents include eptifibatide, clopidogrel, dipyridamole, ticlopidine, and tirofiban. Eptifibatide and tirofiban decrease platelet aggregation by inhibiting glycoprotein II b/III a. Dipyridamole decreases platelet aggregation by inhibiting phosphodiesterase enzyme and inhibit adenosine uptake to cause coronary vasodilatation. Clopidogrel and ticlopidine decreases platelet aggregation by inhibiting binding of ATP to platelet. Action uses, dosage, and side effect of all these drugs are also covered in this chapter.