Which anticoagulant is matched to the mechanism of AntiThrombin Activation?

Heparin is an anticoagulant that works primarily by activating antithrombin, a protein in the blood that inhibits thrombin and factor Xa, both key components in the blood clotting process. When heparin binds to antithrombin, it causes a conformational change that significantly enhances antithrombin's ability to inactivate thrombin and factor Xa. This interaction effectively reduces the formation of fibrin, a critical protein in blood clot formation, thereby demonstrating its mechanism of action through the activation of antithrombin.

Other anticoagulants listed have different mechanisms. Warfarin acts by inhibiting vitamin K epoxide reductase, which impacts the synthesis of vitamin K-dependent clotting factors but does not involve antithrombin activation. Hirudin, a direct thrombin inhibitor, works by directly inhibiting thrombin without involving antithrombin. Fondaparinux is a synthetic pentasaccharide that also activates antithrombin but only inhibits factor Xa rather than thrombin. Therefore, while both heparin and fondaparinux activate antithrombin, heparin's broader mechanism of action and ability to inhibit both thrombin and factor Xa make it the most fitting answer regarding antithrom