antithrombotic therapy Flashcards
what can an arterial thrombosis in the peripheral circulation cause?
claudication, rest pain, gangrene
what are the risk factors for arterial thrombosis?
Smoking Hypertension Diabetes Hyperlipidaemia Obesity / sedentary lifestyle
what drugs are used to treat arterial thrombosis?
Aspirin
LMWH or Fondaparinux
Thrombolytic therapy: streptokinase tissue plasminogen activator
clopidogrel, prasugrel, ticagrelor
what are circumstantial causes of venous thrombosis?
Surgery Immobilisation Oestrogens: OC, HRT Malignancy Long haul flights
What are the genetic causes of venous thrombosis?
Factor V Leiden (5%) PT20210A (3%) Antithrombin deficiency Protein C deficiency Protein S deficiency
what is the treatment for venous thrombosis?
Initial Low molecular weight heparin, s/c od weight adjusted dose Then oral warfarin for 3-6 months (3 months for provoked and 6 months for spontaneous) Or DOAC (instead of warfarin) for 3-6 months, e.g. Rivaroxaban 15mg bd initially then 20mg od
How does heparin work?
anticoagulant
Binds to antithrombin and increases its activity
Indirect thrombin inhibitor
what is LMWH?
unfractionated heparin that is depolymerised and therefore smaller and so can be given subcut (unfractionated needs to be given by continuous infusion and is not used as often)
How does aspirin work?
antiplatelet
Inhibits cyclo-oxygenase irreversibly
Act for lifetime of platelet, 7-10 days
Inhibits thromboxane formation and hence platelet aggregation
how is warfarin given?
orally
How does warfarin work?
inhibits post-translational modification of factors II, VII, IX and X
What is the antagonist of warfarin?
vitamin K
What is the disadvantage of using vit K as an antidote?
doesn’t work on modified clotting factors that are already in the circulation, only starts to work after the liver has synthesised new clotting factors
What is the usual target range INR for warfarin?
2-3
What is the target range of warfarin for people with a prosthetic heart valve?
4-5
