What are the most important pharmacologic characteristics of specific parenteral and oral anticoagulants that are licensed for use in Europe and North America?
What determines the choice of anticoagulant in the prevention and treatment thromboembolism?
What determines the choice of anticoagulant in the management of patients with acute coronary syndromes?
Unfractionated heparin and coumarins were discovered more than 60 years ago and for more than 40 years they were the only anticoagulants available to hospitalists. Now in 2011, several new anticoagulants have been licensed for clinical use and many more are under development. The increase in the number of licensed anticoagulants has expanded the choices available for physicians and patients but has also created new challenges in selecting the optimal therapeutic strategy. Anticoagulant drugs differ in their route of administration, speed of onset and offset of anticoagulant effect, half-life, reversibility, route of excretion, and availability of an antidote, and hospitalists need to be familiar with the properties of individual anticoagulant drugs in order to select the best agent for a particular clinical situation.
The first part of this chapter briefly reviews the most important pharmacologic characteristics of parenteral and oral anticoagulants that are licensed for use in Europe and North America. The second part of this chapter considers the choice of anticoagulant in the prevention and treatment of thromboembolism and management of patients with acute coronary syndromes and illustrates these choices using selected patient scenarios.
Rapidly acting parenteral drugs, such as heparin, have been used for the prevention and initial treatment of thromboembolism during revascularization procedures, whereas the slower-acting oral vitamin antagonists (eg, warfarin) have been used for long-term use. Low molecular weight heparin, fondaparinux and bivalirudin have replaced heparin for many indications, and new oral anticoagulants, including the direct thrombin inhibitor dabigatran etexilate, and the factor Xa inhibitors rivaroxaban and apixaban have begun to replace vitamin K antagonists for long-term use. Dabigatran has been licensed for treatment of atrial fibrillation in Europe and North America and both dabigatran and rivaroxaban have been approved in North America and Europe for the prevention of venous thromboembolism. Apixaban has been approved in Europe for the prevention of venous thromboembolism but is not yet approved for this indication in North America.
Figure 261-1 lists the parenteral anticoagulants, subdivided according to their pharmacologic target, that are licensed for use in Europe and North America. The pharmacologic properties of these agents are summarized in Table 261-1.
Parenteral anticoagulants that are licensed for use in Europe and North America, subdivided according to their pharmacological target. (LMWH, low-molecular-weight heparin.)
Table 261-1 Comparison of the Pharmacologic Characteristics of the Parenteral Anticoagulants, Unfractionated Heparin, Low-Molecular-Weight Heparin, Fondaparinux, and the Direct Thrombin Inhibitors, Bivalirudin and Argatroban