(THER) Heparin Anticoagulants II [Warfarin] Flashcards
(32 cards)
The structure of warfarin is very similar to the structure of…
Vitamin K (that is how it is able to block its functioning).
When would we use heparin vs warfarin?
Heparin = ER or places where we need more rapid onset
Warfarin = chronic care usage
Also, heparin can be used in pregnancies. warfarin CANNOT!
What is the route of administration for Warfarin?
PO
What accounts for the long half-life of warfarin?
It is due to binding to plasma albumin (warfarin is about 97% bound)
Where is warfarin metabolized?
Liver (CYP3A4)
What is one way that diet can affect oral anticoagulant function?
If a patient eats dark leafy greens, they’ll get exogneous vitamin K. Warfarins function is predicated on blocking the body’s endogenous vitamin K formation so this diet will render warfarin near useless.
How can antibiotics interact with warfarin function?
Antibiotics kill gut flora which is used by the body for vitamin K formation. A drop in vitamin K by antibiotics + the drop in vitamin K from warfarin may cause issues of bleeding.
Describe the teratogenicity of warfarin
It can cross the placental barrier and cause fetal bone malformation.
Coumadin induced necrosis
Among other effects, warfarin can also impair the functionality of protein C. This can paradoxically, cause a drop in anti-coagulation causing thrombosis.
Treatments for oral anticoagulant overdose (3)
- Replacement of 4 factors. Infusion of whole fresh blood or frozen plasma
- Recombinant factor VIIa
- Vitamin K
What is the function of vitamin K ? (2)
- It is essential to the attachment of a calcium binding functional group to prothrombin protein.
- Co-factor for the functional synthesis of clottable coagulation factors II, VII, IX and X
Name the new oral anticoagulants (3) and their general mechanism of action (2)
-
Anti-Xa agents
- Rivaroxaban (Xarelto)
- Apixiban
-
Antithrombin Agents
- Dabigatran
Rivaroxaban Target
Factor Xa
Rivaroxaban renal clearance percentage
65%
Rivaroxaban interactions
potent CYP3A4 inhibitors
Apixiban target
Factor Xa
Apixiban renal clearance percentage
25%
Apixiban interactions
potent CYP3A4 inhibitors
Dabigatran target
Factor IIa (thrombin)
Dabigatran renal clearance percentage
100%
Dabigatran interactions
proton pump inhibitors
What is the half-life of rivaroxaban/apixiban/dabigatran compared to warfarin (general terms)?
Compare their coagulation monitering
Signficantly shorter
No need (or ability) to moniter anything but warfarin
Warfarin MOA
Competitive antagonist of vitamin K. Suppresses the synthesis of functional forms of factors II, VII, IX and X
Warfarin monitoring
prothrombin time/ INR
