title: Oral vitamin K1: an option to reduce warfarin's activity.
abstract: OBJECTIVE
  To report 6 patients taking oral vitamin K1 (phytonadione) to reduce warfarin's activity.
  
  
  METHODS
  Six patient cases are summarized in which oral vitamin K1 was used to reduce the international normalized ratio (INR) in patients at risk of bleeding.
  
  
  CONCLUSIONS
  The use of oral vitamin K1 to antagonize warfarin's effects is discussed, as well as the benefits of oral vitamin K1 administration and the disadvantages of parenteral vitamin K1 administration. In addition, an extensive literature review of the discovery and clinical development of warfarin and vitamin K1 is described.
  
  
  CONCLUSIONS
  In patients receiving warfarin therapy who have an increased INR and are at risk of bleeding, oral vitamin K1 therapy may be safer, less painful, and more cost-effective than the traditional parenteral route of administration.
authors.affiliation: Ann Arbor Veterans Affairs Medical Center, MI, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Harrell
authors.forename: S S
authors.initials: SS
authors.lastname: Kline
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000925:Anticoagulants / Q000009:adverse effects / Q000037:antagonists & inhibitors*; D000933:Antifibrinolytic Agents / Q000008:administration & dosage* / Q000266:history / Q000494:pharmacology; D005260:Female; D049673:History, 20th Century; D006801:Humans; D007020:Hypoprothrombinemias / Q000139:chemically induced / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D010837:Vitamin K 1 / Q000008:administration & dosage* / Q000266:history / Q000494:pharmacology; D014859:Warfarin / Q000009:adverse effects / Q000037:antagonists & inhibitors*
chemical_list: D000925:Anticoagulants; D000933:Antifibrinolytic Agents; D014859:Warfarin; D010837:Vitamin K 1