Anticoagulants 

The formation of a stable blood clot (hemostasis) is followed by the orderly breakdown of the clot (fibrinolysis) as wound healing proceeds. A fine balance must be achieved between the activation of hemostatic mechanisms to prevent bleeding and excessive activation, which can cause intravascular thrombosis and embolism (blood vessel occlusion).

The blood clotting cascades have the effect of amplifying a stimulus for coagulation, so it is essential that blood clotting is restricted to the site where it is needed. Random blood clotting in the circulation is normally prevented by the presence of anticoagulant factors. The capillary endothelium is the main source of anticoagulant factors.

The main Anticoagulant factors

( 1 ) Antithrombin III 

• inhibits coagulation by binding to activated factor X and thrombin. 

( 2 ) Heparin 

• released endogenously from mast cells and basophils, and is widely used as an anticoagulant drug. Heparin functions by augmenting the anticoagulant effects of antithrombin III. 

( 3 ) Thrombomodulin 

• inhibits coagulation by binding to thrombin.