Anticoagulation: 0.5 mg vitamin K iv effectively reversed INR >5.0.

Clinical bottom line (level 4)

  1. Patients on warfarin with INR >5.0 who had 0.5 mg vitamin K iv compared with 1.0 mg were more likely to have a therapeutic INR at 24 hours (NNT = 2 at 48 days) and less likely to have INR <2.0 (NNT = 2 at 48 hours) .
Shetty et al: Thrombosis and Haemostasis 1992; 67 (1): 13-15
Expires June 2003

The study

Prospective cohort study with objective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.
Setting: acute hospital, UK

31 patients (aged range 44 to 82 years, 58% female) on warfarin for various medical conditions with INR >5.0

Excluded if
  • active bleeding
  • severe hepatic disease


Control Group: (n = 10, 10 analysed): vitamin K iv 1 mg
Experimental Group: (n = 21, 21 analysed): vitamin K iv 0.5 mg

100% followed for 48 hours

The evidence

Outcome Time to outcome CEREERRRR
(95% CI)		ARR
(95% CI)		NNT
(95% CI)
non-therapeutic INR 48 hours 5
(50.0%)		 19
(90.5%)		 81%
(18% to 96%)		 40%
(7.0% to 74%)		 2
(1 to 14)
INR <2.0 48 hours 5
(50.0%)		 0
(0.00%)		 100%
(% to %)		 50.0%
(19.0% to 81.0%)		 2
(1 to 5)

All patients given 0.5 mg vitamin K had a therapeutic INR at 48 hours.

No side-effects were noted. No patient had thrombotic or haemorrhage complications.

    Citation

    1. Shetty HG, Backhouse G, Bentley DP, et al: Effective reversal of warfarin-induced excessive anticoagulation with low dose vitamin K1. Thrombosis and Haemostasis 1992; 67 (1): 13-15
    Search Terms: reference in review article
    Contributor: Chris Ball and Clare Wotton, June 2000
    Reviewer:

    Clinical Question.
    Patient require warfarin
    Intervention or Exposure vitamin K 0.5 mg
    Comparison vitamin K 1 mg
    Outcome therapeutic INR