1. Switching from VKA (Warfarin) to a DOAC
-Peak onset of action of new agents occurs within 2 to 3 hours
-D/c the VKA, monitor PT/INR and initiate the DOAC when INR is ≤ 2.0
-Remember the resolution of the warfarin effect may take several days.
2. Switching from DOAC to VKA (Warfarin)
-Remember that the full effect of the VKA does not occur for the first few days despite prolongation of the PT/INR.
Dabigatran to Warfarin
Overlap the two agents. The number of days of overlap depends on the patient’s renal function.
CrCl ≥ 50 – Start VKA 3 days b4 you d/c Dabigatran
CrCl 30 to 50 – Start VKA 2 days b4 you d/c Dabigatran
CrCl 15 to 30 – Start VKA 1 day before you d/c Dabigatran
Rivaroxaban or Apixaban to Warfarin – Prescribing package insert suggests stopping rivaroxaban or apixaban and beginning both a parenteral agent and warfarin at the time of the next dose of either of these DOACs would have been taken. The parenteral therapy should be continued for ≥5 days and until INR ≥2 for ≥24 hours, according to the American College of Chest Physicians. They suggest this approach because they say the INR cannot be monitored adequately during the administration of a direct factor Xa inhibitor.
However, some studies show that you can overlap Rivaroxaban and Warfarin as well. See how to do that here.
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Note: While checking INR when switching from Warfarin to a DOAC is recommended, it is not recommended to check INR when a patient is on a DOAC and you are switching them to a VKA (warfarin). DOACs are known to affect (prolong) INR, aPTT, PT, but not in any predictable manner. As such, none of them can be used to monitor DOACs. In fact, DOACs don’t need monitoring.
“The recommendation for switching to warfarin in a patient treated with dabigatran is to start warfarin 3 days prior to stopping dabigatran. Dabigatran is known to increase the INR, so the INR will not reflect warfarin’s effect until dabigatran has been withheld for at least 2 days.” ABFM
[One way to remember the switching between Warfarin and DOACs is that, they DOACs are new and were created to help solve the problems associated with using Warfarin. So they are created for people to move from Warfarin onto them. So that transition from the old to the new is easy. But going from the new to the old is possible but is not as easy.]
Reference
Click to access 0.0-AnticoagulantsfinalPpt.pdf
http://www.pharmacytimes.com/contributor/lindsey-parker-bs-pharmd-candidate-2017/2016/08/how-to-switch-from-xarelto-to-warfarin
Burnett AE, et al. Guidance for the practical management of the direct oral anticoagulants (DOACs) in VTE treatment. J Thromb Thrombolysis. 2016; 41: 206–232.
Moore KT, et al. Switching from rivaroxaban to warfarin: an open label pharmacodynamic study in healthy subjects. Br J Clin Pharmacol. 2015;79(6):907-917.