Blood Thinners Flashcards
(41 cards)
Whats anti-coagulants are prescribed to pts after an MI?
Aspirin - forever
Clopidigrel - 12mths
What is the MoA of the cyclo-oxygenase inhibitor aspirin?
Inhibits COX-1 to stop the formation of thromboxane A2 from arachadonic acid.
Therefore inhibits plt aggregation irreversibly for the lifespan of the plt (7-10 days).
State two indications for aspirin
- Secondary prevention of stroke and TIA
- Secondary prevention of ACS
- Prevention of an MI in stable angina or peripheral vascular disease
- Post PPCI and stent
What is the non-analgesic dose of aspirin?
75mgs
700mgs for analgesia
Name an ADP/P2Y12 receptor antagonist
Clopidigrel
Prasugrel
What is the MoA of ADP receptor antagonists?
Irreversibly stops ADP from activating plts via the P2Y12 receptor.
This prevents the activation of GPIIb/IIIa receptors by calcium.
Clopidigrel has a slow onset of action. How can this be overcome?
Loading dose
Name a glycoprotein IIb/IIIa inhibtor
Abciximab
Tirofiban
What is the MoA of GPIIb/IIIa inhibitors?
Blocks the receptors, to prevent the binding of fibrinogen.
Abciximab binds irreversibly, and has >80% reduction in aggregation.
Tirofiban binds reversibly.
State a side effect of GPIIb/IIIa inhibitors
Thrombocytopenia
Name a phosphodiesterase inhibitor
Dipyridamole
What is the MoA of phosphodiesterase inhibitors?
Inhibits phosphodiesterase to prevent the breakdown of cAMP and cGMP. This keeps intracellular calcium low to prevent plt activation.
Inhibits cellular uptake of adenosine, leading to more adenosine in the plasma. This inhibs TXA2 receptors to inhibit activation.
State two indications for dipyridamole
- Secondary prevention of stroke of TIA +/- aspirin.
- Adjuct to other anti-coagulants in pts with prosthetic heart valves.
Name four antiplatelets
Aspirin
Clopidigrel
Abiximab
Dipyridamole
Name a fibrinolytic
Streptokinase
Alteplase
Tenecteplase
What is the MoA of fibrinolytics?
Activates plasminogen
Why can streptokinase be given acutely for coronary artery occlusion, but can’t be given repeatedly?
Antigenic - immune system will mount response
What is the MoA of warfarin?
Inhibs the reduction of vitamin K to it active form.
Therefore vitK can’t be used to make the clotting factors II (prothrombin), VII, IX and X.
Why does warfarin take a few days to take effect?
Circulating clotting factors are still active.
Takes a few days for them to be cleared.
Therefore need heparin cover for the first few days if anticoagulation is needed immediately.
Warfain is a racemic mixture. What is this?
Has equal amounts of left and right handed enantiomers
What is the half-life of warfarin?
36-48hrs
State three indications of warfarin
DVT and PE prophylaxis and treatment
AF with high risk of stroke
Protein C and S deficiency
Following a major surgery with long stasis e.g. orthopaedic
State three effects of drug-drug interactions that increase the INR reading (increased risk of bleeding) and give three example drugs
- Inhibition of CYP2C9 e.g. amiodarone, clopidigrel, binge alcohol, metronidazole
- Inhibition of platelet function e.g. aspirin
- Reducing vitK production by eliminating gut bacteria e.g. cephlosporin antibiotics
- Reducing vitK absorption from the gut e.g. NSAIDs
- Displacement from albumin by other drugs e.g. sodium valproate
Why should pregnant women avoid warfarin?
Crosses the placenta.
In the first trimester it’s teratogenic.
In the third trimester can cause brain haemorrhage.
