What is the antidote for warfarin (Coumadin) overdose?

• A. Vitamin K
• B. Protamine sulfate
• C. Aminocaproic acid
• D. Naloxone

Answer: (A)

Warfarin slows clotting by blocking recycling of vitamin K, which is needed to make the clotting factors II, VII, IX, and X. Giving vitamin K replenishes the body's supply and enables the liver to resume producing these vitamin K–dependent factors, reversing the anticoagulant effect. In a bleeding emergency, intravenous vitamin K is used for faster reversal, often along with fresh frozen plasma or prothrombin complex concentrate to provide the factors immediately.

The other options aren’t antidotes for warfarin: protamine sulfate reverses heparin, not warfarin; aminocaproic acid helps with certain bleeding disorders but doesn’t specifically reverse warfarin’s effect; naloxone reverses opioid overdose, not anticoagulation.