What is the mechanism of action of heparin in anticoagulation therapy?

Heparin’s mechanism of action in anticoagulation therapy primarily involves the activation of antithrombin III, a naturally occurring anticoagulant protein in the body. By enhancing the activity of antithrombin, heparin effectively leads to the inactivation of several key coagulation factors, particularly thrombin (factor IIa) and factor Xa. This reduction in thrombin and factor Xa levels decreases the ability of the blood to form clots, providing an antithrombotic effect.

When heparin binds to antithrombin, it induces a conformational change that significantly increases antithrombin’s ability to inactivate these coagulation factors. The inhibition of thrombin is particularly important because thrombin not only converts fibrinogen to fibrin (a critical step in clot formation) but also plays a role in platelet activation and the overall clotting cascade. Similarly, by inhibiting factor Xa, heparin prevents the generation of thrombin from prothrombin, effectively blocking the clotting process at an early stage.

This understanding of heparin’s mechanism clarifies its role in preventing and treating various thromboembolic disorders, as well as its use during procedures such as surgery or in patients at risk