Anticoagulants and antiplatelets Flashcards
Example of oral anticoagulant
Warfarin
What does warfarin do
Vitamin K antagonist
Mechanism of action of warfarin
1) New factor formed from liver (it is a precursor)
2) new factor is chemically modified (still the precursor)
3) Precursor undergoes in the coagulation cascade
4) The system is Vitamin K dependent
5) Therefore warfarin blocks Vitamin K reductase which is needed for Vitamin K fo act as a cofactor
6) Therefore the production of the proper coagulation factors is inhibited by warfarin
How long does warfarin take ti impact on the production of coagulation factors
3 days
what is warfarin used for
- In patients with replaced heart valves
- Atrial fibrillation
- DVT
What is the dose of warfarin determined by
INR
What does the INR measure
Anticoagulation of the patient
What are examples of injectable anticoagulants
Unfractionated heparin
Low molecular weight heparins eg enoxaparin
Difference between warfarin and enoxaparin
Enoxaparin acts immediately
What does enoxaparin do
Activates antithrombin III which inactivates some clotting factors and thrombin by complexing with serine protease of the factors (interferes with coagulation factors)
What is the use of heparin
Used to prevent thrombosis and used to prevent blood clotting on collection
When is heparin particularly used
Used whilst warfarin takes effect because warfarin takes 3 days to take effect
What are DOACs
Drugs which directly inhibit the coagulation factors
Benefits of DOACs
Fewer complications and less drug reactions
Drawback of DOACs
Warfarin is reversible but DOACs are expensive and challenging to reverse ie if the patient is bleeding and you want to reverse it
