8.1: Antiplatelet And Anticoagulant Therapy Flashcards
(20 cards)
How does warfarin work?
Inhibits the production of vitamin K dependent clotting factors 2, 7, 9, 10
What would a patient with previous Hx of DVT/ PE/ AF who is on warfarin, aim for an INR range between?
2 to 3
DVT = on warfarin for 3 to 6 months PE = on warfarin for 6 months AF = on warfarin until risk > benefits
What are some adverse effects of warfarin?
Teratogenic
Bleeding (epistaxis, intracranial haemorrhage, GI bleeding-> anaemia)
What is Virchow’s triad?
Abnormal constituents of blood eg on OCP, smoker, malignancy
Abnormal flow
Abnormalities in vessel walls
Why does heparin need to be given initially to a patient commencing warfarin therapy?
Due to its slow onset of action, due to turnover of clotting factors
How long before surgery does warfarin need to be stopped?
3 days
Due to its slow onset of action, half life approx 48 hours
How can warfarin be monitored in patients?
PT time
INR
Extrinsic pathway factors
What are some drugs that can potentiate warfarin?
Will they increase or decrease the INR?
Alcohol, aspirin, NSAIDs, amiodarone, metronidazole, quinolone, cephalosporin abx
Increase INR
What are some drugs that will inhibit warfarin?
Will they increase or decrease the INR?
Antiepileptics, except Na valproate
Rifampicin
St Jons Wort
They will decrease the INR
How can warfarin therapy be reversed, eg in a px with major bleed?
Stop warfarin (don’t restart until INR <5)
IV vitamin K (slow)
Fresh frozen plasma (fast)
Which factor do heparins activate?
Anti thrombin 3 (to inactivate Xa)
UF heparin can also inactivate thrombin (as it as a longer chain to can bind to both molecules, unlike LMWH)
LMWH affect Xa specifically
How are the types of heparin given?
Heparin must be given parentally due to poor GI absorption
UF heparin given IV
LMWH given SC
What are some adverse effects of heparin?
Bruising and bleeding
Thrombocytopenia
Osteoporosis
Why is LMWH more favourably?
Does not require monitoring unless UFH
How can heparin be reversed if a px is bleeding?
Stop heparin
Give protamine
What type of drugs are apixaban and rivaroxaban?
DOACs
What types of drugs are enpxaparin and dalteparin?
LMWH
What scoring system can be used to decide whether to commence a patient on an anticoagulant by assessing their stroke risk?
CHA2DS2VASc
Treat anyone with a score of 2 or more with anticoagulants
How does aspirin work?
Via COX1 inhibition
Why can the fibrinolytic drug streptokinase only be used once?
As it’s a bacterial protein so it antigenic
So the body generated blocking antibodies to it which persist for many years
