Anti-platelets Flashcards
Name the types of anti-platelets
Cyclo-oxygenase inhibitor
P2Y12/ADP receptor inhibitor
Glycoprotein IIb/IIIa inhibitor
Phosphodiesterase inhibitor
Fibrinolytic agents
When should antiplatelets be used and what do they do
Antiplatelets shuold be used on platelet rich, arterial thrombi
Antiplatelets inhibit platelet aggregation -> prevent arterial thrombus formation
How do cyclo-oxygenase inhibitors work
Cyclo-oxygenase inhibitors prevent COX-1 from forming thromboxane A2 to prevent aggregation
Irreversible inhibition - inhibition lasts as long as the platelet lifespan
Action at low dose has antiplatelet effects while at high doses has an analgesic effect
Name a cyclo-oxygenase inhibitor
Aspirin
Name some indications for the use of a cyclo-oxygenase inhibitor
Secondary prevention of stroke and TIA if other agents contraindicated
Secondary prevention of actue coronary syndrome
Post primary percutaneous coronary intervention and stent to reduce ischaemic complications
Secondary prevention of MI in stable angina and peripheral vascular disease
How do P2Y12/ADP receptor antagonists work and give some examples
These inhibit binding of ADP to P2Y12 receptors to inhibit activation of GPIIb/IIIa receptors
E.g. clopidogrel, prasugrel, ticagrelor
Describe when clopidogrel is used
Clopidogrel has slow mode of action without a loading dose
It reduces mortality and morbidity post thromboembolic stroke
Reduces secondary events post MI
Prophylaxis in patients intolerant to aspirin
Typically used for 12mths post MI
How do glycoprotein IIb/IIIa inhibitors work and give some examples
These drugs target the binding of fibrinogen and vWF, and also target the final common pathway to compete with platelet aggregation
E.g. abciximab, tirofiban, eptifbatide
Describe how abciximab works
Abciximab is a monoclonal antibody that irreversibly blocks GPIIb/IIIa receptors to prevent fibrinogen bidning
Causes >80% reduction in aggregation but has high risk of bleeding
Slow to dissociate -> gives long mode of action
What is a side effect of GPIIb/IIIa inhibitor use
Thrombocytopenia
How do phosphodiesterase inhibitors work
Inhibit cellular reuptake of adenosine so have increased plasma adenosine which inhibits platelet aggregation via A2 receptors
Acts as phosphodiesterase inhibitor to prevent cAMP and cGMP degradation which inhibits expression of GPIIb/IIIa
Name a phosphodiesterase inhibitor
Dipyridamole
Name some uses and side effects of phosphodiesterase inhibitors
Uses: secondary prevention of ischaemic stroke and TIAs. Prophylaxis of thromboembolism following valve replacement
Side effects: vasodilation causing flushing and headaches. Hypersensitivity
How do fibrinolytic agents work
Fibrinolytic agents wok by dissolving the firbin meshwork of the thrombus to break the clot down
Given either IV or IA
Name some fibrinolytic agents
Streptokinase - antigenic -> given once
Alteplase
Reteplase
