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DOAC - Assessing for suitability to switch from warfarin to a DOAC

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Why this page is important: I once made a mistake when reviewing a patient who was having various problems with warfarin and recommending they switch to a DOAC, only to later find that they are unsuitable due to their kidney function. Another time, I went so far as to refer them to the local anticoagulation clinic for a switch and then realised they were overweight deming them unsuitable for the switch. How embarassing! I learned from these mistakes and made a check list which I follow when assessing a patient's suitability for continuing with warfarin.

Checklist 

Assessment

Recommendation

Is anticoagulation still appropriate and required

For example, can anticoagulant therapy be stopped in patients with prior DVT / PE, where the risk of recurrence is now considered low

seek specialist advice if necessary

Is patient's condition suitable for DOAC switch

DOACs are only licensed for the prevention of atrial fibrillation (AF)-related stroke in people with non-valvular AF and for the treatment and secondary prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE)

there is little data on DOACs for patients with venous thrombosis at unusual sites (e.g. portal vein thrombosis) and these patients should be discussed with an anticoagulation specialist

DOACs should not be considered for patients 

  • with moderate to severe mitral stenosis
  • with antiphospholipid antibody syndrome (APLS)
  • who are pregnant, breastfeeding or planning a pregnancy
  • with active malignancy/ chemotherapy (unless advised by a specialist)
Does patient require a higher INR than the standard INR range of 2.0 – 3.0 DOACs are not suitable 
Does patient have a severe renal impairment  Not recommended in patients with Creatinine Clearance (CrCl) < 15ml/min
Check interacting medications 

Click here for information about DOAC interactions 

check with HIV drug interactions website at https://www.hiv-druginteractions.org/

some antiepileptics- phenytoin, carbamazepine, phenobarbitone or rifampicin are likely to reduce DOAC levels so should be discussed with an anticoagulation specialist

on triple therapy (dual antiplatelet therapy plus warfarin) without discussing with an anticoagulant specialist or cardiologist

Extremes of bodyweight < 50kg or > 120kg

When calculating CrCl for these patients in primary care: adjusted BW for >120kg and actual BW for ​<50kg ​

Usually unsuitable for DOAC

CHADVASC score 

 

Creatinine clearance 

Reduce dose if CrCL< 50 CrCl dosing

For patients in whom DOACs are suitable

 If all above is suitable and the decision is made to switch to a DOAC then you will need to

  1. Choose appropriate DOAC for choosing the right DOAC click here
  2. Choose the correct dose for DOAC doses click on this link
  3. Plan the switch for switching from warfarin to a DOAC click here
  4. Ensure patent understands everything about the switch for a checklist of counselling points for the patient click here

For patients in whom DOACs are NOT suitable

  1. is self-testing of INR with a CoaguChek self-testing meter a possibility? There are limited supplies of Coaguchek self-testing meters available in the UK but, where available, these should be used for appropriate patients continuing warfarin therapy.
  2. assess if Low Molecular Weight Heparin (LMWH) is suitable - Whenever possible, patients with mechanical heart valves should remain on warfarin, however if monitoring is impossible then a brief period of LMWH could be considered if the patient can be taught to self-inject or a family member that lives with them can administer the injection; Dosing recommendations should be provided by the patient’s current anticoagulation service provider by phone or electronically. See https://www.nice.org.uk/guidance/dg14

 

 

 

 

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