What is the mechanism of action for heparin?

Heparin functions primarily by inactivating thrombin, which is a key enzyme in the coagulation process. It does this through its interaction with antithrombin III, a serine protease inhibitor. When heparin binds to antithrombin III, this complex undergoes a conformational change that significantly enhances the ability of antithrombin to inhibit thrombin and factor Xa. This effectively reduces the generation of fibrin and inhibits the clotting cascade, leading to its anticoagulant effects.

Understanding this mechanism is crucial for its clinical application, particularly in preventing and treating thromboembolic disorders. By directly targeting thrombin and other factors within the coagulation pathway, heparin plays a vital role in managing situations where excessive clot formation can lead to serious complications.