Effect of prolonged coumadin treatment on the production of pulmonary metastases in the rat

To evaluate the effect of prolonged anticoagulant treatment using Coumadin (warfarin sodium) on the production of pulmonary metastases, 455 rats with Walker 256 carcinosarcoma were given either water or Coumadin solution ab lib in addition to their chow. Administration of Coumadin for 10 days resulted in a significant decrease in metastases from 85.8% of the control group to 9.8% of the Coumadin-treated animals (P < 0.001). The survival of these animals also was increased from 3.8% to 42.6% at 9 weeks. No excessive bleeding occurred in any of these animals though the prothrombin time was prolonged more than twice the average value observed in the normal rat.