title: A practical approach to minimize the interaction of dietary vitamin K with warfarin.
abstract: OBJECTIVE
  The many interactions between warfarin and other drugs and foods generate great challenges for clinicians and patients in maintaining stable anitcoagulation. Interactions due to variable vitamin K content of different dietary items influence the therapy of nearly all patients on warfarin. Unfortunately, there is no widely acceptable, patient-friendly strategy for managing such interactions. In this contribution, we propose a practical approach to managing this troublesome interaction, consisting of 'maintaining constant weekly dietary vitamin K intake scores'.
  
  
  METHODS
  Twenty-three vitamin K-rich vegetables commonly seen in Taiwanese meals were identified and classified into seven score grades according to their relative vitamin K content per serving. The scores were based on published vitamin K content of different foods.
  
  
  CONCLUSIONS
  The vitamin K score was equivalent to 5 points for spinach and garland chrysanthemum per bowel, followed by (baby) bok choy, amaranth, arden lettuce (4 points); leaf mustard, edible rape, sweet potato leaf, bai cai and Chinese leek (3 points); and okra and Chinese celery (0·5 points). This classification can be used to guide patients in recording their weekly vitamin K scores with a view to maintaining it when on warfarin.
  
  
  CONCLUSIONS
  We suggest a novel approach to patient counselling on warfarin to maintain consistent dietary vitamin K intake and achieve a more stable anticoagulation response. A prospective randomized controlled trial to validate this pragmatic approach would be useful.
authors.affiliation: Institute of Clinical Pharmacy and Pharmaceutical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: C-H
authors.initials: CH
authors.lastname: Chang
authors.forename: Y-W
authors.initials: YW
authors.lastname: Wang
authors.forename: P-Y
authors.initials: PY
authors.lastname: Yeh Liu
authors.forename: Y-H
authors.initials: YH
authors.lastname: Kao Yang
mesh_terms: D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects; D001777:Blood Coagulation / Q000187:drug effects; D004032:Diet; D018565:Food-Drug Interactions; D006801:Humans; D008297:Male; D013624:Taiwan; D014675:Vegetables; D014812:Vitamin K / Q000008:administration & dosage* / Q000009:adverse effects; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D000925:Anticoagulants; D014812:Vitamin K; D014859:Warfarin
keywords: diet; interaction; vitamin K; warfarin