Which medication blocks the availability of vitamin K and reduces the risk of stroke, venous thrombosis, or pulmonary embolism?

Which medication blocks the availability of vitamin K and reduces the risk of stroke, venous thrombosis, or pulmonary embolism?

• A. Aspirin
• B. Warfarin
• C. Heparin
• D. Clopidogrel

Answer: (B)

Warfarin is a vitamin K antagonist that blocks the availability of vitamin K by inhibiting the enzyme vitamin K epoxide reductase. This prevents the regeneration of active vitamin K, leading to reduced production of the vitamin K–dependent clotting factors II, VII, IX, and X (and proteins C and S). With fewer functional clotting factors, the blood’s ability to form clots decreases, which lowers the risk of stroke in conditions like atrial fibrillation and also reduces the risk of venous thrombosis and pulmonary embolism. Initiation often requires bridging with heparin because the effects of warfarin aren’t immediate, and INR monitoring is necessary to maintain a therapeutic range. It’s important to keep vitamin K intake consistent and be mindful of drug and dietary interactions that can affect warfarin’s effectiveness. Antiplatelet drugs like aspirin and clopidogrel work by inhibiting platelets, not vitamin K–dependent clotting factors, and heparin works through antithrombin to inhibit thrombin and factor Xa.

Warfarin is a vitamin K antagonist that blocks the availability of vitamin K by inhibiting the enzyme vitamin K epoxide reductase. This prevents the regeneration of active vitamin K, leading to reduced production of the vitamin K–dependent clotting factors II, VII, IX, and X (and proteins C and S). With fewer functional clotting factors, the blood’s ability to form clots decreases, which lowers the risk of stroke in conditions like atrial fibrillation and also reduces the risk of venous thrombosis and pulmonary embolism.

Initiation often requires bridging with heparin because the effects of warfarin aren’t immediate, and INR monitoring is necessary to maintain a therapeutic range. It’s important to keep vitamin K intake consistent and be mindful of drug and dietary interactions that can affect warfarin’s effectiveness.

Antiplatelet drugs like aspirin and clopidogrel work by inhibiting platelets, not vitamin K–dependent clotting factors, and heparin works through antithrombin to inhibit thrombin and factor Xa.