Vitamin K improved anticoagulation stability for patients taking warfarin.
In a double blind, randomized study published in the Blood First Edition Paper, 70 patients treated with warfarin and having unstable anticoagulant control received a 150 µg/d oral vitamin K or placebo for six months. Stability of anticoagulation was measured and compared to measurements taken six months immediately prior to the study.
Anticoagulation control improved in 33 out of 35 patients receiving vitamin K supplementation and, of these, 19 fulfilled criteria for having stable control of anticoagulation. Of 33 patients, only 24 receiving placebo demonstrated some degree of improvement, with only seven of these fulfilling the criteria for having stable control.
Researchers concluded concomitant supplementation of vitamin K, can significantly improve anticoagulation control in patients with unexplained instability of response to warfarin.
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.
HEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY:
Elizabeth Sconce, Peter Avery, Hilary Wynne, and Farhad Kamali
Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin
Blood, Mar 2007; 109: 2419 - 2423.
Blood First Edition Paper Epub online, Nov. 16, 2006