Warfarin therapy: INR took between 5 and 8 days after discontinuation to reach 1.2.

Clinical bottom line (level 2b)

  1. In patients on warfarin, the international normalised ratio took between 5 and 8 days after warfarin discontinuation to become less than 1.2.
White et al: Annals of Internal Medicine 1995; 122 (1): 40-42
Expires June 2003

The study

Prospective cohort study with ?objective ?blinded outcomes, not adjusted for confounding factors, not validated in an independent set of patients.
Setting: university medical centre anticoagulation clinic, USA

22 patients (aged range 25 to 81 years; mean 55, 55% male) patients on warfarin who are considered low risk for thrombosis if they have several days without anticoagulation. Patients were considered low risk if they had:
  • deep vein thrombosis after 12 weeks of treatment
  • atrial fibrillation with no valvular heart disease, stroke or systemic embolisation
  • congestive cardiomyopathy without heart failure, previous stroke or systemic embolisation


Excluded if
  • complex dosing regimen that precluded simplification
  • history of widely fluctuating warfarin requirements


    • Note:
  • Nine patients had atrial fibrillation, ten had venous thromboembolism and three had cardiomyopathy.


    • Control Group: (n = , analysed):
    Experimental Group: (n = , analysed):
    Patients received a fixed daily dose of warfarin at 5 pm. After at least a week of this regimen, each patient was seen midday on a Monday (day 1), and his or her international normalised ratio (INR) was measured. Patients then discontinued warfarin therapy and to return on day 3, day 5 and day 8 for repeated INR measurements.
    100% followed for 8 days

    The evidence

  • Three days after the last dose of warfarin, 10 out of 22 patients (45%) had an INR greater than 1.5, and 2 out of 22 (9%) had an INR less than 1.2.
  • On day 5, all but five patients had an INR less than 1.2.
  • On day 8, 20 patients (91%) had INRs less than 1.2 (one other had an INR of 1.2 and one 1.23).
  • The mean initial INR was 2.6 mg/d (range 1.95 to 3.8).

    • Citation

    1. White RH, McKittrick T, Hutchinson R, et al: Temporary discontinuation of warfarin therapy: Changes in the international normalized ratio. Annals of Internal Medicine 1995; 122 (1): 40-42
    Contributor: Clare Wotton and Musab Hayatli, June 2000
    Reviewer: Martin Dawes

    Clinical Question.
    Patient on warfarin and low risk for thrombosis
    Intervention or Exposure discontinuation of warfarin
    Outcome international normalised ratio