 Erythrocyte flexibility is not affected by normal doses of ancrod.The rheological changes are readily maintained and the viscosity approaches pretreatment values very slowly (within about 10 days) after stopping ancrod.One of the cleavage fibrinogen products, termed 'desAA-Fibrin', acts as cofactor for the tPA-induced plasminogen activation and an increased fibrinolysis results in return (profibrinolytic activity of ancrod).