title: Low-dose vitamin K to augment anticoagulation control.
abstract: OBJECTIVE
  To determine the effect of daily low-dose oral vitamin K supplementation on reducing variations in the international normalized ratios (INRs) in patients taking warfarin.
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  Anticoagulation clinic in a large, private-practice hematology group.
  
  
  METHODS
  Eight motivated patients (three men, five women), aged 45-79 years, receiving anticoagulant therapy with warfarin, whose INRs had been fluctuating for reasons not associated with identifiable changes in diet, warfarin dosage, activity level, illness, or changes in drug therapy.
  
  
  METHODS
  Daily supplementation with oral vitamin K, starting with 100 microg/day
  
  
  RESULTS
  Anticoagulation providers monitored INR responses; all documented INR values were included in the analysis, even those intentionally allowed outside the therapeutic range when dosages were adjusted for procedures. After dietary vitamin K supplementation, INR fluctuations diminished in nearly all patients. Overall, a significant decrease was noted in the INR standard deviation (p<0.05), and more INRs were in the therapeutic range after the start of supplementation. Allowing for small fluctuations on either side of the target range, the number of INRs within 0.2 units of the target range increased from 32% to 57% (relative increase 76%). Time in range also increased by a similar degree.
  
  
  CONCLUSIONS
  Supplementation with daily low-dose oral vitamin K significantly increased the number of INRs in range as well as the time in range, and decreased INR fluctuation in this small series of selected patients.
authors.affiliation: College of Pharmacy, University of Texas, Austin, and the Anticagulation Clinics of North America, San Antonio, Texas, USA. a.reese@usip.edu
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Reese
authors.forename: Lisa E
authors.initials: LE
authors.lastname: Farnett
authors.forename: Roger M
authors.initials: RM
authors.lastname: Lyons
authors.forename: Bhavin
authors.initials: B
authors.lastname: Patel
authors.forename: Laura
authors.initials: L
authors.lastname: Morgan
authors.forename: Henry I
authors.initials: HI
authors.lastname: Bussey
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage*; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014812:Vitamin K / Q000008:administration & dosage*; D014859:Warfarin / Q000008:administration & dosage*
chemical_list: D000925:Anticoagulants; D014812:Vitamin K; D014859:Warfarin