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Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin

Lookup NU author(s): Elizabeth Sconce, Dr Peter Avery, Dr Hilary Wynne, Professor Farhad Kamali


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Patients receiving warfarin who have unstable control of anticoagulation have a significantly lower intake of dietary vitamin K compared with their stable counterparts. We hypothesized that supplementation with oral vitamin K would improve stability in patients with previously unstable control of anticoagulation. Seventy warfarin-treated patients with unstable anticoagulation control were randomly assigned in a double-blinded fashion to receive a daily amount of 150 μg oral vitamin K or placebo orally for 6 months. Measures of stability of anticoagulation control in the 6-month study period were compared with those in the 6 months immediately prior to it. Vitamin K supplementation resulted in a significantly greater decrease in standard deviation of international normalized ratio (INR) compared with placebo (-0.24 ± 0.14 vs -0.11 ± 0.18; P < .001) and a significantly greater increase in percentage time within target INR range (28% ± 20% vs 15% ± 20%; P < .01). Anticoagulation control improved in 33 of 35 patients receiving vitamin K supplementation; of these, 19 fulfilled our criteria for having stable control of anticoagulation. However, only 24 of 33 patients receiving placebo demonstrated some degree of improvement, with only 7 patients fulfilling the criteria for having stable control. Concomitant supplementation of vitamin K, perhaps through reducing the relative day-to-day variability in dietary vitamin K intake, can significantly improve anticoagulation control in patients with unexplained instability of response to warfarin. © 2007 by The American Society of Hematology.

Publication metadata

Author(s): Sconce E, Avery P, Wynne H, Kamali F

Publication type: Article

Publication status: Published

Journal: Blood

Year: 2007

Volume: 109

Issue: 6

Pages: 2419-2423

ISSN (print): 0006-4971

ISSN (electronic): 1528-0020

Publisher: American Society of Hematology


DOI: 10.1182/blood-2006-09-049262

PubMed id: 17110451


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