Anti-platelet and anti-coagulant drugs Flashcards
How do platelets bind to collagen to form a clot?
They have glycoproteins of their cell surface
GP1a adheres directly to VWF
GP1b adheres via receptors to VWF
GP2b and GP3a form the GP2b3a complex that also binds via receptors to Von Willebrand Factor
What are some examples of anti-platelet agents?
Aspirin
Clopidogrel
Prasugrel
Abciximab
Eptifibatine
How does aspirin work?
Usually, platelets release thromboxane A2
This sticks to receptors on the platelet surface
This allows platelet aggregation
Thromboxane A2 is formed from COX
Aspirin blocks COX so prevents thromboxane A2 formation
How does Clopidogrel and Prasugrel work?
They are ADP-receptor antagonists
ADP is released from platelets
It binds to P2Y12 receptors on the surface
This allows for platelet aggregation
Clopidogrel and Prasugrel block and antagonise these receptors
How does Abciximab and Eptifibatine work?
They block the GP2b3a receptor
This prevents platelet binding to Von Willebrand Factor so stops aggregation and clot formation
Who are clopidogrel and prasugrel usually used in?
It is mostly used in those with angina or with a past history of myocardial infarction
What is warfarin?
An anti-coagulant
How does warfarin work?
Warfarin blocks the enzyme Vitamin K Epoxide Reductase
This allows for vitamin K production
Vitamin K carboxylates Clotting factors and prothrombin
This usually adds the negative charge that allows it to bind to the Ca2+ ions of the platelet surface
Warfarin prevents binding of these to the platelets, therefore preventing coagulation
What is required for warfarin patients?
Constant INR (International Normalised Ratio) blood tests to monitor levels, and check dosages
How do thrombin inhibitors work?
They inhibit thrombin, and so prevent fibrin production and the amplification loop
Give an example of a thrombin inhibitor?
Dabigatran
What is an activated factor 10 inhibitor (Factor Xa)?
A drug that inhibits factor Xa which in turn, blocks the conversion of prothrombin to thrombin
What are some examples of a Factor Xa inhibitor?
Apixaban
Edoxaban
Rivaroxiban
What are the uses of TPA infusions?
They increase levels of Tissue Plasminogen Activator
This converts plasminogen to plasmin
Plasmin breaks down fibrin into D-dimers or Fibrin Degradation Products
What are the risks of TPA infusions?
They greatly increase the risk of bleeding, so are given only when the reward outweighs the demand
