Vitamin K is used as a reversal agent for which medication?

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

Answer: (C)

Vitamin K reverses the anticoagulation effect of Warfarin. Warfarin blocks the enzyme that regenerates active vitamin K, leading to reduced production of the vitamin K–dependent clotting factors II, VII, IX, and X. Supplying vitamin K allows the liver to resume making these factors, counteracting Warfarin’s effect. The reversal is slower with oral vitamin K and faster with IV, and in serious bleeding you’d often use fresh frozen plasma or prothrombin complex concentrates for rapid correction. Vitamin K isn’t used to reverse heparin (protamine sulfate is used) or antiplatelet drugs like clopidogrel or aspirin, which don’t depend on vitamin K–dependent factor synthesis for their effect.