The quantitative reduction by acute-dose warfarin of venous thrombosis in normal and hyperthrombotic rats.

Warfarin was tested for its relative ability to reduce thrombosis in two series of rats. In one series both the warfarin and control animals were made hyperthrombotic by an infusion of ellagic acid just before thrombosis was measured. In the second series (termed normothrombotic) no thrombotic stimulant was given. In all, 179 test and 109 control animals were used. Warfarin was given in varying doses to the test animals. Ellagic acid was administered as a single standard dose. At operation, two test animals and one control of similar weight were operated on concurrently. Thrombosis was measured by the weight of thrombus occurring on a standard 2 cm intravenous platinum wire in one hour. In optimum dose, warfarin reduced thrombus formation by 74% in the unstimulated series and by 83% in the hyperthrombotic one, when the mean factor II levels were 18% and 19% respectively. The residual thrombus under warfarin treatment was, however, greater in the hyperthrombotic than in the unstimulated animals at all levels of factor II. Best correlation of thrombus weight was with factor II in unstimulated animals.