Warfarin Mechanism of Action

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson goes over the important concepts behind warfarin's mechanism of action. First, you'll learn the basics of blood clotting and then how warfarin disturbs this process.

Definition

What compound is used to kill rats but save human lives? It's warfarin! Also known as Coumadin by its brand name. Warfarin is a type of blood thinner that's properly called an anticoagulant, which helps minimize or disturb the proper clotting of blood. It's a very commonly used oral medication.

Warfarin under the brand name Coumadin
warfarin

This lesson goes over this drug's mechanism of action.

Clotting

In order to understand how warfarin works, you need to know how clotting works! The complete mechanism behind the way your blood clots is extremely complex, but it goes something like this.

Your blood contains quasi-cells called platelets. They're not true cells, but they look like cells. When a blood vessel is healthy, platelets slide past the blood vessel's walls with ease. As soon as a blood vessel is injured, the platelets stick to the injured part of the wall and to one another, thereby plugging up the injured portion of the blood vessel so blood doesn't escape!

This mass of platelets is further reinforced by a net of fibrin strands. Fibrin is a type of protein critical to the formation of strong blood clots.

Now, pay serious attention. There is an enzyme involved in all this process. It's called thrombin and it does two important things with respect to this entire process:

  1. It helps the platelets to stick to one another.
  2. It helps to form fibrin.

Now, there are certain proteins involved in the making of the enzyme thrombin.

Warfarin's Role

And here is where we transition to warfarin's role in all of this. Warfarin's main mechanism of action lies in its ability to stop the synthesis of vitamin K-dependent factors. It does so by blocking something called the vitamin K epoxide reductase (VKORC1) enzyme complex. Since that term is a gigantic headache to read and sound out, think of it more simply like this:

VKORC1's job is to change a form of vitamin K into a new form that can help in activating clotting proteins. Warfarin works by blocking VKORC1. Since the enzyme can't work, it can't use vitamin K to help make these vitamin K dependent factors.

These vitamin K dependent factors, which are types of proteins, are:

  • Factor II
  • Factor VII
  • Factor IX
  • Factor X
  • Proteins C and S

The proteins called Factors II, VII, IX, and X, are all eventually involved in the formation of thrombin either directly or indirectly. In other words, the production of these vitamin K-dependent factors is minimized when warfarin is used. So warfarin is basically a big wrench you're throwing into the process.

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