Warfarin & anti-coagulants Flashcards
When is the ideal time to check INR and give warfarin?
INR checked at 9am and dose administered at 6pm
What does the INR measure?
Value is derived from prothrombin time which measures the extrinsic pathway of coagulation
What is a normal INR in the absence of anti-coagulation?
0.8-1.2
What INR value gives a risk of bleeding?
INR>5
What INR value gives a risk of clotting?
INR<0.5
What is the target INR for warfarinised patients?
2.5
What is the half life of warfarin?
35-40 hours, thus is taken once daily
What agent is used to reverse the effects of warfarin?
Vitamin K
Can warfarin be used in pregnancy? Are there alternatives?
Contraindicated in pregnancy
Heparin is safe to use in pregnancy and while breastfeeding
What are some medications that should be avoided whilst taking warfarin?
Aspirin, tramadol and NSAIDs can increase the risk of bleeding
What checks should be done prior to commencing warfarin?
Drug history, allergies, LFTs, renal function and thyroid function
How long does warfarin take to reach maximum effect?
5-10 days
When is rapid loading of warfarin done?
To treat PE, DVT or mechanical prosthetic cardiac valve insertion
What is given with warfarin during rapid loading?
LMWH is started to provide anticoagulant cover during rapid loading, continuing until the INR is within therapeutic range for 2 consecutive days
What dose of warfarin is given when rapid loading?
10mg initially then tapered according to INR
When is slow loading of warfarin done?
In non-acute settings e.g. AF where immediate anticoagulation is not required and the INR can be stabilised within 3-4 weeks
What dose is warfarin started in patients in non-acute settings?
1-3mg daily then the INR checked weekly until stable
The daily dose is increased once per week by 1mg per day until INR reached 2.5
Name some direct Xa inhibitors
Apixaban, rivaroxaban, edoxaban
Name some direct thrombin inhibitors
Dabigatran, etexilate
What is the preferred injectable/parenteral anticoagulant and why?
LMWH is preferred to unfractionated heparin due to the lower risk of HIT
What tests should be done prior to starting LMWH?
INR, APTT, platelets and LFTs
How is stroke managed if they present within 4.5 hours?
Thrombolysis with IV alteplase
CT scan must be done prior to this to rule out haemorrhage
How is stroke managed after initial therapy?
300mg aspirin should be started daily for 2 weeks within 24 hours of thrombolysis or within 48 hours of symptom onset
After these 2 weeks, switch to clopidogrel 75mg daily
