Journal of Thrombosis and Thrombolysis

, Volume 24, Issue 1, pp 23–27

Prospective study of supplemental vitamin K therapy in patients on oral anticoagulants with unstable international normalized ratios

  • Sarah K. Ford
  • Caron P. Misita
  • Betsy Bryant Shilliday
  • Robert M. Malone
  • Charity G. Moore
  • Stephan Moll
Article

DOI: 10.1007/s11239-007-0014-z

Cite this article as:
Ford, S.K., Misita, C.P., Shilliday, B.B. et al. J Thromb Thrombolysis (2007) 24: 23. doi:10.1007/s11239-007-0014-z

Abstract

Background

It is not known whether patients on oral vitamin K antagonists who have unstable INRs achieve more stable INRs with daily vitamin K supplementation. We sought to determine whether vitamin K supplementation may decrease INR variability in patients with a history of unstable INRs, how soon the INR decreases after vitamin K therapy is initiated, the time to reach a therapeutic INR after vitamin K initiation, and how much of an increase in oral anticoagulant dose is needed to maintain the INR in the desired range.

Methods

This is a prospective open label crossover study of patients on warfarin with a history of fluctuating INRs. A 9 week observation phase was followed by an 8 week period with patients receiving 500 μg of oral vitamin K daily. INRs were determined once weekly with a home point of care monitoring instrument.

Results

Vitamin K supplementation led to a decrease in INR variability in five of the nine patients studied (56%). INR decrease occurred 2–7 days after initiation of vitamin K. Therapeutic INRs were achieved 2–35 days after vitamin K therapy was initiated and an increase in warfarin dose of 6–95% was required to bring the INR back into the therapeutic range.

Conclusions

INR fluctuations may decrease in selected patients with unstable INRs who receive vitamin K supplementation. A study with a larger sample size and longer follow-up period is needed. The results of the present study can help design such a study.

Keywords

Fluctuation INR Vitamin K Warfarin 

Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Sarah K. Ford
    • 1
  • Caron P. Misita
    • 2
  • Betsy Bryant Shilliday
    • 3
  • Robert M. Malone
    • 3
  • Charity G. Moore
    • 3
  • Stephan Moll
    • 2
  1. 1.Department of PharmacyUniversity of North Carolina HospitalsChapel HillUSA
  2. 2.Department of Medicine, Division of Hematology-OncologyUniversity of North Carolina Medical CenterChapel HillUSA
  3. 3.Department of Medicine, Division of General MedicineUniversity of North CarolinaChapel HillUSA