Effect of 200 μg/day of vitamin k1 on the variability of anticoagulation control in patients on warfarin: A randomized controlled trial

Habeeb Majeed, Marc Rodger, Melissa Forgie, Marc Carrier, Monica Taljaard, Dimitrios Scarvelis, Carol Gonsalves, Rosendo A. Rodriguez, Philip S. Wells

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Background Controversy exists whether low-dose vitamin K supplementation can improve anticoagulation control in patients with unstable anticoagulation under warfarin. In a single- centre randomized, double-blind, placebo-controlled study, we evaluated the effectiveness of 200 μg/day of vitamin K1 in patients with unstable control under warfarin. Methods Effectiveness of Vitamin K1 supplementation was primarily assessed by the percentage (%) of Time-in-Therapeutic-Range (TTR) and secondarily by the standard deviation (SD) of the patient's INR values; the proportion of out-of-range INRs; and the number of dose changes on warfarin. Their change scores were obtained by subtracting the mean value in the 6 months pre-randomization from the mean value in the 6 months post-randomization. Multivariable linear-regressions identified factors associated with anticoagulation instability. Results Fifty out of 54 patients were analyzed (intervention: n = 26; placebo: n = 24). Most indications (87%) for anticoagulation were venous thromboembolism (VTE). The intervention was associated with a greater reduction in the change scores for the SD of INRs between the pre and post-randomization periods compared with placebo. The mean change score was -0.259 ± 0.307 with the intervention and -0.046 ± 0.345 with placebo (p = 0.026). There was no effect on the change scores of the (%) TTR (p = 0.98), the number of INRs out-of-range (p = 0.58) and the number of dose changes (p = 0.604). Factors independently associated with increased variability in the SD of INRs were increased alcoholic drinks/week (p = 0.017), dosing errors (p = 0.0009) and missed INR appointments (p = 0.035). Conclusion Vitamin K1 supplementation reduces the SD of INRs as an indicator of the variability in anticoagulation control in patients treated with warfarin for VTE.

Original languageEnglish
Pages (from-to)329-335
Number of pages7
JournalThrombosis Research
Volume132
Issue number3
DOIs
StatePublished - Sep 2013
Externally publishedYes

Keywords

  • Anticoagulation
  • Double-blind
  • Randomized
  • Thrombosis
  • Vitamin K antagonists
  • vitamin K

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