01-04-2015, 05:50 AM
NBME 6
A 29 y/o woman receives a dose of warfarin orally for a large deep venous thrombus of the right leg. She is currently taking an oral contraceptive. Her prothrombin time is 12 sec (INR 1.0). Two hours after the administration of warfarin, her prothrombin time remains 12 sec (INR 1.0). Which of the following best explains why this patient's prothrombin time did not change?
A ) Oral contraceptives accelerate the clearance of warfarin
B ) The large thrombus increases the dose of warfarin required
C ) Prothrombin time is not a measure of the efficacy of warfarin
D ) Preexisting circulating coagulation factors have not been cleared
E ) Warfarin should have been administered intravenously
A 29 y/o woman receives a dose of warfarin orally for a large deep venous thrombus of the right leg. She is currently taking an oral contraceptive. Her prothrombin time is 12 sec (INR 1.0). Two hours after the administration of warfarin, her prothrombin time remains 12 sec (INR 1.0). Which of the following best explains why this patient's prothrombin time did not change?
A ) Oral contraceptives accelerate the clearance of warfarin
B ) The large thrombus increases the dose of warfarin required
C ) Prothrombin time is not a measure of the efficacy of warfarin
D ) Preexisting circulating coagulation factors have not been cleared
E ) Warfarin should have been administered intravenously
Thanks