COAGULANTS AND ANT-COAGULANTS

COAGULANTS AND ANT-COAGULANTS

Coagulation of blood involves the formation of fibrin by a complex phenomenon. The clotting factors are the proteins synthesized by the liver. Some of the factors (II or prothrombinVII, IX and X) are vitamin K dependent for the final stage of their synthesis in the liver. In the process of clotting, each factor undergoes partial proteolysis to forman enzyme (factor Xa). The activated factor then brings about similar proteolysis of the next factor, leading ultimately to conversion offibrinogen into soluble fibrin and finally, conversion of soluble fibrin into insoluble fibrin (firm clot). The other substances aid the factors in the process of coagulation. The coagulation proceeds along either intrinsic system or extrinsic system. All the reactions necessary for the intrinsic system are already present in the blood in inactive form. The initiators of the extrinsic system are not generally present in the blood; they are added by tissue injury. The intrinsic pathway is a slow pathway and minutes are required for the formation of activated factor Xa. In case of extrinsic pathway, the factor Xa is generated within seconds.

Blood clots are removed from the vascular system by breakdown of fibrin by proteolytic enzyme plasmin or fibrinolysin which is formed from its inactive precursor proplasmin or profibrinolysin.The blood clotting factors are fibrinogen (I), prothrombin (II), mboplastin (III), ionic calcium (IV), hereditary labile factor (V), accelein (VI), proconvertin (VII), antihemophilic factor (VIII), plasma,  thromboplastin component (IX). Stuart Prower factor (X), plasma thromboplastin antecedant (XI). Hageman factor (XII) and fibrin stabilizing factor (XIII).

COAGULANTS

Haemorrhagic state is caused by vascular defects, platelet defects, plasma coagulation disorder or low prothrombin concentration.Coagulants are used to treat  severe haemorrhage Vitamin K, (phytomenadione ) maintains a normal concentration of prothrombin and other clotting factors in blood plasma. This vitamin is used as an antihaemorrhagic agent. Protamine and thrombin are the other official drugs

ANTCOAGULANTS

It is employed as prophylactics and in the treatment of thrombo-embolic occlusine vascular diseases such as cardiac infraction, pulmonary embolism and venous thrombosis and to prevent thrombosis after operation or by other neans.

Heparin inhibits the formation of thrombin from prothrombin, and fibrin from fibrinogen and thus retards the coagulation. The other anticoagulant drugs are coumarins and indanediones (phenindione).