Which is NOT a warfarin reversal agent?

• A. Vitamin K
• B. Fresh Frozen Plasma
• C. Four-factor PCC
• D. Idarucizumab

Answer: (D)

Understanding how to reverse warfarin boils down to replenishing the vitamin K–dependent clotting factors that warfarin suppresses. Warfarin blocks vitamin K–epoxide reductase, lowering factors II, VII, IX, and X, so reversal strategies aim to restore those factors quickly. Vitamin K helps the liver resume production of these factors, but it can take hours to days. In urgent bleeding, giving fresh frozen plasma or a four-factor prothrombin complex concentrate provides the needed clotting factors directly, producing faster correction with PCC often preferred for its rapid action and smaller volume.

Idarucizumab, by contrast, is the antidote for dabigatran. It binds dabigatran and neutralizes its effect but has no activity against warfarin’s mechanism. Therefore it does not reverse warfarin anticoagulation, whereas the other options listed are appropriate reversal strategies for warfarin-associated bleeding.