A 63-year-old man with a history of atrial fibrillation visits the clinic for evaluation of his current medications. His physician orders laboratory tests including prothrombin time.
Which one of these drugs is used to reduce the possibility of blood clotting in this patient through its action on the enzyme epoxide reductase?
A- Aspirin
B- Dipyridamole
C- Heparin
D- Streptokinase
E- Warfarin
Answer
This patient takes warfarin to reduce the possibility of blood clotting which is a common complication of atrial fibrillation. Warfarin acts by inhibiting the enzyme epoxide reductase which is responsible for converting vitamin K into active form. Most of the clotting factors are dependent on vitamin K to participate in thrombosis. Aspirin and dipyridamole act by inhibition of platelet aggregation. Heparin is used in emergencies by increasing the activity of antithrombin III which inhibits thrombin and other coagulation factors. Streptokinase acts by converting plasminogen into plasmin which results in digesting fibrin clots.
The correct answer is E