Warfarin Flashcards
(23 cards)
What is warfarin?
An oral anticoagulant, used to prevent thrombus formation in the veins, less so in the arteries
Warfarin, acenocumaol and phenindione are examples of what? What do they do?
Coumarins and Phenidiones
They antagonise vitamin K
It takes at least 48-72 hrs to get the full anticoagulation effect (WAR-farin takes the longest)
For an immediate anticoagulation effect what should we give?
Give unfractionated heparin or LMWH
Warfarin has how many strengths and what are the box colours?
4 strengths
0.5mg =white
1mg=Brown
3mg=Blue
5mg =Pink
What’s the warfarin antidote?
Phytomenidoine (vitamin K kills warfarin)
What foods and drinks should we watch out for?
Cranberry juice
Pomegranate Juice (increases INR)
Avoid diet changes (liver,sprouts,brocoli,green tea,salads and leafy greens)
Alcohol and heavy drinking, decreases the effects of warfarin
Can warfarin be used in pregnancy?
NOOOOO!!!
Warfarin,Acenoncoumol,phemidione = should be avoided completely in pregnancy
All of them cross the placenta- fatal abnormalities so should be avoided in the 1st/3rd trimester especially during the last few weeks and delivery
Risk of haemorrhage is common and increases with vitamin k DEFICIENCY
What are the 2 MHRA warnings for warfarin?
1) Calciphylaxis - Painful rash, common in patients with renal disease
- Refer to GP
2)Miconazole( or Daktarin oral gel)
- Causes bleeding, stop and seek medical attention
- unexplained bleeding or bruising, nose bleeds or blood in urine
INR values within 0.5 are satisfactory, which ones have a 2.5 target?
Treatment of DVT or PE
AF
Cardioversion
Dilated cardiomyopathy
Mitral stenosis regurgitation
Acute arterial embolism
What has a 3.5 target?
Recurrent DVT
Mechanical prosthetic heart valve
Indication and dose
Initially 5-10mg on Day 1, subsequent doses dependent on prothrombin time
When can lower induction dose be given?
Lower induction dose can be given over 3-4 weeks in patients who do not require anticoagulation
What’s the dose for elderly
Elderly patients are given a lower induction dose - maintenance 3-9mg daily to be taken the same time each day
MAJOR BLEED, What do we do when on warfarin?
Stop warfarin
Phytomenadione (Vitamin K) by slow IV injection. And/ Or Dried prothrombin complex/fresh frozen prothrombin which is less effective
If INR is more than 8 and no bleeding?
Stop warfarin
Phytomenadione, slow IV injection, repeat dose if INR is still high after 24 hrs
Restart when the INR is less than 5
INR 5-8, Minor bleed
Stop warfarin
Phytomenadione( vitamin K)
Slow IV injection
And restart when INR is less than 5
INR 5-8 NO bleed (these come up every year bissshh!!!!)
Withdraw 1 or 2 doses of warfarin, then reduce the subsequent maintenance dose
Important interactions to note and what they do to warfarin?
Miconazole, other anti fungals (fluconazole, itraconazole) = increase the effects of warfarin
St John’s wart = Decreases the effects of warfarin
Alcohol =Decreases the effect of warfarin
Amiodarone = Increases the effects of warfarin
Aspirin = Increases the risk of bleeding
Bezafibrate = increases the effects of warfarin Aspirin
Carbamazepine= decreases the effect of warfarin
Fluconazole + warfarin?
Increases anticoagulant effect, monitor INR and adjust the dose
Warfarin and clarithromycin
Increases the anticoagulant effect of warfarin, manufacturers advice - monitor INR and adjust the dose
What juice do we avoid?
Cranberry and pomegranate juice, they increase the anticoagulant effect
Green leafy veg and tea?
Major diet changes will change the anticoagulant effect
