Question 1

How do you remember Warfarin?

Accepted Answer

Warfarin breaks down as WAR = war + FARIN = far in. Break warfarin into WAR and FAR IN. Imagine you are far in a long war. The way you win a war is by cutting off the enemy's supply lines, and here the critical supply is vitamin K. Warfarin blocks vitamin K, so the clotting factors never get activated. The war takes place in 1972 to represent factors 2, 7, 9, 10. War far in, block the K supply.

Question 2

What class of drug is Warfarin?

Accepted Answer

Warfarin is a Vitamin K Antagonist • Oral Anticoagulant.

Question 3

How is Warfarin tested on the USMLE?

Accepted Answer

Warfarin blocks vitamin K epoxide reductase, so the liver can't activate the vitamin K-dependent clotting factors (2, 7, 9, 10) and proteins C and S. Its effect is delayed for days because circulating factors must be degraded first, and it is monitored with PT/INR.

Question 4

A patient with a new DVT is started on warfarin and bridged with heparin. During the first few days, warfarin transiently increases his clotting risk before it becomes protective. What best explains this early prothrombotic effect?

Accepted Answer

A - Proteins C and S are natural anticoagulants that are also vitamin K-dependent, and they have shorter half-lives than factors 2, 9, and 10. When warfarin starts, C and S drop before the procoagulant factors do, leaving a brief window of increased clotting, which is why patients are bridged with heparin and can rarely develop warfarin skin necrosis. B and D are the wrong direction, and C misstates the reason for bridging.

Warfarin

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