title: Effect of 200μG/day of vitamin K1 on the variability of anticoagulation control in patients on warfarin: a randomized controlled trial.
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).
  
  
  CONCLUSIONS
  Vitamin K1 supplementation reduces the SD of INRs as an indicator of the variability in anticoagulation control in patients treated with warfarin for VTE.
authors: The University of Ottawa, Department of Medicine, The Ottawa Hospital Research, Institute, Ottawa, Ontario, Canada.
authors: Habeeb
authors: H
authors: Majeed
authors: Marc
authors: M
authors: Rodger
authors: Melissa
authors: M
authors: Forgie
authors: Marc
authors: M
authors: Carrier
authors: Monica
authors: M
authors: Taljaard
authors: Dimitrios
authors: D
authors: Scarvelis
authors: Carol
authors: C
authors: Gonsalves
authors: Rosendo A
authors: RA
authors: Rodriguez
authors: Philip S
authors: PS
authors: Wells
mesh_terms: D000925:Anticoagulants / Q000008:administration & dosage*; D004311:Double-Blind Method; D004357:Drug Synergism; D005260:Female; D005838:Genotype; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D010919:Placebos; D011110:Polymorphism, Genetic; D013927:Thrombosis / Q000188:drug therapy*; D016896:Treatment Outcome; D010837:Vitamin K 1 / Q000008:administration & dosage*; D014859:Warfarin / Q000008:administration & dosage*
chemical_list: D000925:Anticoagulants; D010919:Placebos; D014859:Warfarin; D010837:Vitamin K 1
keywords: Anticoagulation; Double-blind; Randomized; Thrombosis; Vitamin K antagonists; vitamin K