Heparin inhibits the clotting of blood and the formation of fibrin clots both in vitro and in vivo. In combination with a co-factor, it inactivates thrombin thus preventing the conversion of fibrinogen to fibrin. Heparin also prevents the formation of a stable fibrin clot by inhibiting the activation of the fibrin stabilizing factor.
Heparin Sodium inhibits reactions which lead to clotting but does not alter the normal components of the blood. Although clotting time is prolonged by therapeutic doses, bleeding time is usually unaffected. Heparin Sodium does not have flbrinolytic activity, therefore it will not lyse existing clots.