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Appropriate and Safe Conversion from Warfarin to a DOAC 

Introduction

Any patient who is admitted to hospital and is taking warfarin (or any other coumarin anticoagulant e.g. phenindione, acenocoumarol) should be considered for switching to a direct oral anticoagulant (DOAC). This recommendation is based on the reduced bleeding risk with DOACs when compared with warfarin and improved patient acceptability given the lack of need for ongoing monitoring in hospital and community-based clinics.

Suitable patients for switching from warfarin to a DOAC

Suitable patients for switching from warfarin (or any other coumarin anticoagulant e.g. phenindione, acenocoumarol) to a DOAC (e.g. apixaban, edoxaban) must meet both of the following criteria:

  • The patient has an indication for anticoagulation with a DOAC.
  • The patient has no contraindications to receiving a DOAC.

Indications for which a DOAC can be used

Situations when patients should NOT be switched from warfarin

  • INR target >2.5
  • Pregnant or breastfeeding women
  • Creatinine clearance (CrCl) <15ml/minute 
  • Patients >150kg
  • Mechanical heart valves
  • Severe mitral stenosis
  • Concurrent use of specific medications (see below)
  • Patients previously switched from a DOAC to warfarin (or any other coumarin anticoagulant)
  • Liver disease associated with cirrhosis and/or coagulopathy
  • Clear indication for choice of warfarin e.g. recent significant bleed
  • Triple positive antiphospholipid syndrome with previous venous thrombosis i.e. lupus anticoagulant (LA) + anticardiolipin (ACL) + anti beta 2 glycoprotein 1 (B2-GP1). If a patient is LA and ACL positive, but anti B2-GP1 has not been measured, they should be considered triple positive.

Concurrent Medicines

If switching to apixaban, concurrent use of the following should be avoided:

  • Triazole and imidazole antifungals (except fluconazole)
  • Strong CYP3A4 and P-gp inhibitors, e.g. ciclosporin, dronedarone, erythromycin, ketoconazole or protease inhibitors.
  • Strong CYP3A4 and P-gp inducers, e.g. rifampicin, phenytoin, carbamazepine, phenobarbital or St John's Wort.

 

If switching to edoxaban:

  • Use with caution and reduce dose to edoxaban oral 30 mg once daily with the following concurrent medicines:
    • Ciclosporin, dronedarone, erythromycin or ketoconazole.

The above highlighted interactions should not be considered to be an exhaustive list. Further information regarding interactions is available in the BNF and relevant SPC available from https://www.medicines.org.uk/emc/. 

Choice of DOAC and process of switching

Non-valvular atrial fibrillation:

The DOAC of choice is apixaban. See the Summary of Product Characteristics (SPC) for dosing, cautions and contraindication advice. If switching from warfarin to apixaban, discontinue warfarin and start apixaban when INR is <2. 

Venous thrombosis (first or recurrent event):

Refer to Diagnosis and Treatment of Venous Thromboembolism guideline for full information.

Please note: The following dosing guidance is only applicable to patients who have already been receiving warfarin for their venous thromboembolism. For guidance on new initiations, see the Diagnosis and Treatment of Venous Thromboembolism guideline.

  • If the patient is ≤3 months post-thrombosis, discontinue warfarin and start apixaban oral 5mg twice daily when INR is <2.
  • If >3 months post-thrombosis, discontinue warfarin and start apixaban oral 2.5mg twice daily when INR is <2.

Use apixaban with caution if CrCl is 15-29ml/minute. 

Further advice

For further information / advice regarding the process of converting patients from warfarin to a DOAC, please contact the Glasgow and Clyde Anticoagulation Service (GCAS) - see Appendix 6 for contact details.

If you have any questions regarding the appropriateness of a DOAC for an individual patient, please contact a haematologist - see Appendix 6 for contact details.

 

Guideline reviewed: July 2024

Page last updated: August 2024