[Action of venoms on blood coagulation: diagnosis of hemorrhagic syndromes].

Venoms from Viperidae, Crotalidae, some Australian Elapidae and few Colubridae are a mixture of enzymes which impact on blood coagulation in several ways. These proteins can be classified as haemorragins which induce disorders of the capillary permeability, disintegrins and related proteins which disturb the clotting time while acting on plate adhesion, and proteases which cleave peptides. Venoms contain molecules directed against several targets of the coagulation system. The same molecule may present different activities. Components of snake venoms are used in diagnostic coagulation tests, fundamental research and as drugs against infectious agents, cancer or haematological disorders. The structural differences between proteins from snake venoms and natural coagulation factors and the target diversity of the venom components explain why it remains illusory to treat bleedings when acting just at symptom level. Conversely, antivenom, whose components are directed against the venom proteins, is the only aetiological therapy effective against snake envenomations.