THE ANTICOAGULANT, ANTITHROMBOTIC AND HEMORRHAGIC EFFECT OF LONG-TERMWARFARIN ON EXPERIMENTAL VENOUS AND ARTERIAL THROMBOSIS IN THE RAT

The amount of thrombus formed in one hour, on standard platinum wire i n aorta and vena cava of 48 control and 96 warfarin treated Fats of bo th sexes, was measured, Warfarin was given in varying doses (0.1 - 0.1 8 mg/kg) for ten consecutive days before operation to enable the coagu lation factors to stabilize, Factors II, VII and X levels as well as p rothrombin time (PT) values were obtained for each animal, Factor leve ls and PT ratio were related to reduction in arterial and venous throm bus weight. The relation between reduction in thrombus weight and depl etion in coagulation factor levels was best for factor II and fairly g ood for factor X at all levels of anticoagulation, All animals which w ere haemorrhagic had factor II levels of below 15%, with a mean of 8%, At low warfarin dosage a significant reduction of thrombus (>30%) wen t undetected by any test, but was least frequently undetected by facto r II and most frequently undetected by PT, All rats with diminished th rombus had at least one factor depleted, Haemorrhagic animals were fou nd with any PT ratio in excess of unity, Factor II reflected antithrom botic and haemorrhagic effects of warfarin much better than factors X, VII, or PT.