 This leads to a pathologically increased blood viscosity and thereby to a worsening of symptoms of the circulation disorder (more intense pain, decreased mobility of the limb and decreased temperature, need for partial or even total limb amputation).The blood viscosity in patients receiving ancrod is progressively reduced by 30 to 40% of the pretreatment levels.The decreased viscosity is directly attributable to lowered fibrinogen levels and leads to important improvements in blood flow and perfusion of the microcirculation.