2- anticoagulant & antiplatelet drugs Flashcards
what are indications for anticoagulant drugs?
- venous thrombosis
- atrial fibrillation (quiver & make stasis)
*anticoagulant drugs used when bleeding from secondary haemostasis issue, fibrin clot problem
what is heparin mode of action?
it enhances antithrombin - antithrombin binds to thrombin or factor X, switching off complex. heparin wraps around keeping secure so don’t dissociate
what are the 2 forms of heparin and how do you monitor?
unfractionated (old one, needs more monitoring) and low molecular weight heparin
= monitor with aptt (both pt & aptt prolonged but aptt more sensitive)
what are complications of heparin?
main one is bleeding
- also get thrombocytopenia (low platelets from platelets clump together) and osteoporosis on long term (why heparin mostly just used initially)
what is warfarin mechanism of action?
inhibits vitamin K (reminder that vit K gives negative charge to clotting factors II, VII, IX, X so necessary for their function)
why use heparin before warfarin?
warfarin slow to work so use heparin initially (heparin works quick and has worse long term use effects like osteoporosis) so works well
how to monitor warfarin?
INR - has narrow therapeutic window
how do you reverse warfarin effects?
stop warfarin and give vitamin K
*would do this if bleeding side effect
what are the new better anticoagulants that are now used more?
direct thrombin inhibitors e.g. dabigatran (good but not favoured as kidney issues)
factor Xa inhibitors = apixaban, rivaroxaban, edoxaban
= good as oral & no monitoring needed
what is aspirin mechanism of action?
inhibits cyclooxygenase (which is needed for making thromboxane A2 which helps platelets accumulate)
what are side effects of aspirin?
bleeding, block prostaglandin production, GI ulcers, bronchospasm
what is clopidogrel & prasugrel mechanism of action?
(P2Y12) ADP receptor antagonists (platelets bind to collagen via ADP receptors)
what is dipyridamole mechanism of action?
PDE inhibitor, increases cAMP which inhibits platelet aggregation
what is abciximab mechanism of action?
GP IIb/IIIa inhibitor (inhibits aggregation as platelets stick to each other using glycoproteins)
when is it important to stop antiplatelet?
you have to stop anti-platelet agents 7 days before elective operations (as antiplatelet drugs affect fro 7-10 days since lifespan of platelet)
if serious bleeding = can reverse with platelet transfusion
*can also give tranexamic acid in some situations of heavy bleeding (trauma)
