Heparin Anticoagulants II Flashcards
What are the main uses of the oral anticoagulants?
Prophylactic use: Prevention of thrombotic disorders
Therapeutic use: Treatment of established thrombus
What is the main oral anticoagulant?
Warfarin
What are the targets for warfarin action?
Factor II, VII, IX and X
What is the MOA of the coumarins (oral anticoagulants)?
All agents depress the formation of functional forms of factors II (prothrombin), VII, IX and X by inhibiting the ๐-carboxylation of glutamic acid in these proteins which is essential for Ca+2 binding.
How does warfarin inhibit the ๐-carboxylation of glutamic acid?
Inhibits the action of Vitamin K reductase
What is the onset of action of warfarin like?
Slow as it has an effect on the liver with enzyme synthesis
What is the function of Vitamin K?
It is essential for the attachment of Ca2+ binding group to prothrombin and for the synthesis of Factor II/VII/IX/X
What is the oral absorption of warfarin?
All are well absorbed orally
What is the half life of warfarin like?
Long T1/2 of the oral anticoagulants, due to binding to plasma albumin - warfarin is 97% bound
What pathway does warfarin inhibit?
Extrinsic Pathway
What is the therapeutic target with warfarin dosing?
1.5 times the prolongation of the normal bleed time
What is used to monitor warfarin dosing?
PT/INR
What are some factors that can affect warfarin dosing?
- ๔ฐNutrition - too many green leafy vegetables will increase Vitamin K
- Anemia
๔ฐ- Liver disease - will decrease production of clotting proteins so warfarin will have increased activity
๔ฐ- Biliary obstruction ๔ฐ - Drugs
How can drugs cause warfarin potentiation?
a. by causing vitamin K deficiency.
b. by displacing warfarin from protein binding sites.
c. by decreasing clotting-factor synthesis.
How can drugs inhibit the action of warfarin?
a. by decreasing warfarin absorption.
b. by enhancing warfarin metabolism.
