Supplementation with Vitamin K Improves Anti-anticoagualtion Control in People on Warfarin

Daily supplements of vitamin K could help to control anticoagulation in over half the people taking the blood thinning medication warfarin, scientists from the UK have reported.

The new randomised, double-blind, placebo-controlled study looked at the effects of a daily vitamin K supplement (150 micrograms, about twice the RDA) or placebo on anti-coagulation in 70 warfarin treated patients with unstable anticoagulant control.

Fluctuations in anti-coagulation control, measured as a function of standard deviation, were found to have a significantly greater decrease in the vitamin K supplementation group than placebo, despite a significant reduction in the placebo group (decrease of 0.24 versus 0.11, respectively). Out of the 35 patients receiving the supplements, 33 had significantly improved anticoagulation, with 19 of these fulfilling the criteria for having stable control of anticoagulation. On the other hand, only 24 out of 33 patients in the placebo group had some improvement, with seven fulfilling the stable control criteria.

“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,” said the researchers.

The result is particularly important because daily dietary control of vitamin K intake is difficult to maintain and even small changes in vitamin K intake are reported to translate into large variations in the production of clotting factors.

Additionally, because vitamin K is known to participate in blood clotting, people taking blood thinners like warfarin are usually recommended to avoid supplementation with the vitamin.

However, researchers from Newcastle University and the Royal Victoria Infirmary, Newcastle, have built on previous research that reported that unstable control of anti-coagulation is linked to low vitamin K intake (Thrombosis & Haemostasis, Vol. 93, pp. 872-875).

“We hypothesised that supplementation with oral vitamin K would improve stability in patients with previously unstable control of anticoagulation,” explained lead author Elizabeth Sconce in the journal Blood.

Source: Blood First Edition Paper
Published online ahead of print, doi 10.1182/blood-2006-09-049262
“Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin”
Authors: E. Sconce, P. Avery, H. Wynne, and F. Kamali
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=pubmed