RT Book, Section A1 Lichtman, Marshall A. A1 Kaushansky, Kenneth A1 Prchal, Josef T. A1 Levi, Marcel M. A1 Burns, Linda J. A1 Armitage, James O. SR Print(0) ID 1133366292 T1 Principles of Antithrombotic Therapy T2 Williams Manual of Hematology, 9e YR 2017 FD 2017 PB McGraw-Hill Education PP New York, NY SN 9781259642470 LK hemonc.mhmedical.com/content.aspx?aid=1133366292 RD 2024/03/29 AB Antithrombotic agents are characterized separately as anticoagulants (including vitamin K antagonists, heparin or heparin derivatives, and directly acting thrombin or factor Xa inhibitors), antiplatelet agents, or fibrinolytic drugs (see Chap. 86), depending on their primary mechanism, although there is overlap in their activities.Anticoagulant therapy acts to decrease fibrin formation by inhibiting the formation and action of thrombin. Its most common use is in preventing systemic embolization in patients with atrial fibrillation, treatment of acute arterial thrombosis (eg, myocardial infarction or peripheral arterial thrombosis) and for treatment or (secondary) prevention of venous thromboembolism.Anticoagulant therapy is often monitored using coagulation testing because of marked biologic variation in effect.Antiplatelet agents act to inhibit platelet function, and their primary uses are in preventing thrombotic complications of cerebrovascular and coronary artery disease. They also have a role in treatment of acute myocardial infarction. They have no effect in preventing or treating venous thromboembolism.For many agents, the risk-to-benefit ratio is narrow, with the result that bleeding complications occur.Bleeding is the most common adverse effect of anticoagulation (Table 87–1). Consequently, the clinician should carefully weigh the risks and benefits for each patient when selecting treatment.The most common oral anticoagulants are vitamin K antagonists (coumarins). However, recently, new oral anticoagulants with specific antithrombin activity or anti–factor Xa activity have become available and are currently evaluated in clinical trials (see section, “Oral Antithrombin and Anti–factor Xa Agents” below).