antikoagulants

Anticoagulants are medicines that reduce the blood’s ability to form clots. They do not dissolve existing clots but help prevent clot growth and new clots, reducing the risk of stroke, pulmonary embolism, and other thromboembolic complications. They are used in conditions such as atrial fibrillation, venous thromboembolism, and after some surgical procedures.

Anticoagulants fall into several main groups. Vitamin K antagonists, such as warfarin, inhibit the synthesis of vitamin K–dependent clotting factors, shortening the clotting process. Direct oral anticoagulants or DOACs include direct thrombin inhibitors (dabigatran) and direct factor Xa inhibitors (rivaroxaban, apixaban, edoxaban). They provide predictable effects and often do not require routine laboratory monitoring. Heparins come in unfractionated heparin and low-molecular-weight heparin forms; they enhance the activity of antithrombin to inhibit thrombin and factor Xa, with LMWH having a more targeted effect on Xa. Fondaparinux is a synthetic Xa inhibitor that acts through antithrombin.

Monitoring and reversal vary by drug. Warfarin requires regular INR monitoring to maintain a therapeutic range and can be reversed with vitamin K and other agents. DOACs typically do not require routine laboratory monitoring, but kidney function and drug interactions can affect dosing, and specific reversal agents are available for major bleeding (idarucizumab for dabigatran; andexanet alfa for factor Xa inhibitors; PCCs may be used in some settings). Unfractionated heparin can be monitored with the aPTT and reversed with protamine sulfate; LMWH is monitored less often and can be reversed with protamine to a limited extent.

Common risks include bleeding, which can be serious. Heparin-induced thrombocytopenia is a rare but important adverse reaction to heparins. Anticoagulants require careful consideration of drug interactions, dietary Vitamin K intake (notably with warfarin), and patient-specific factors such as age, kidney function, and pregnancy considerations.