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Effect of 200μG/day of vitamin K1 on the variability of anticoagulation control in patients on warfarin: a randomized controlled trial.

  • 2013-09
  • Thrombosis research 132(3)
    • Habeeb Majeed
    • Marc Rodger
    • Melissa Forgie
    • Marc Carrier
    • Monica Taljaard
    • Dimitrios Scarvelis
    • Carol Gonsalves
    • Rosendo A Rodriguez
    • Philip S Wells

Study Design

Type
Randomized Controlled Trial (RCT)
Sample size
n = 54
Population
50 out of 54 patients (intervention: n=26; placebo: n=24) with unstable anticoagulation under warfarin
Methods
Single-centre randomized, double-blind, placebo-controlled study, 200 μg/day of vitamin K1
Blinding
Double-blind
Duration
6 months pre-randomization and 6 months post-randomization

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.

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