Editing Vitamin K (section)

===Managing warfarin therapy===

[[Warfarin]] is an [[anticoagulant]] drug. It functions by inhibiting an enzyme that is responsible for recycling vitamin K to a functional state. As a consequence, proteins that should be modified by vitamin K are not, including proteins essential to blood clotting, and are thus not functional.<ref name="Whitlon" /> The purpose of the drug is to reduce risk of inappropriate blood clotting, which can have serious, potentially fatal consequences.<ref name=Higdon /> The proper anticoagulant action of warfarin is a function of vitamin K intake and drug dose. Due to differing absorption of the drug and amounts of vitamin K in the diet, dosing must be monitored and customized for each patient.<ref name=Gong2011>{{cite journal | vauthors = Gong IY, Schwarz UI, Crown N, Dresser GK, Lazo-Langner A, Zou G, Roden DM, Stein CM, Rodger M, Wells PS, Kim RB, Tirona RG | title = Clinical and genetic determinants of warfarin pharmacokinetics and pharmacodynamics during treatment initiation | journal = PLOS ONE| volume = 6 | issue = 11 | pages = e27808 | date = November 2011 | pmid = 22114699 | pmc = 3218053 | doi = 10.1371/journal.pone.0027808 | bibcode = 2011PLoSO...627808G | doi-access = free }}</ref> Some foods are so high in vitamin K<sub>1</sub> that medical advice is to avoid those (examples: collard greens, spinach, turnip greens) entirely, and for foods with a modestly high vitamin content, keep consumption as consistent as possible, so that the combination of vitamin intake and warfarin keep the anti-clotting activity in the therapeutic range.<ref name="auto1" />

Vitamin K is a treatment for bleeding events caused by overdose of the drug.<ref name=Tomaselli2017 /> The vitamin can be administered by mouth, [[Intravenous therapy|intravenously]] or [[Subcutaneous tissue|subcutaneously]].<ref name=Tomaselli2017>{{cite journal | vauthors = Tomaselli GF, Mahaffey KW, Cuker A, Dobesh PP, Doherty JU, Eikelboom JW, Florido R, Hucker W, Mehran R, Messé SR, Pollack CV, Rodriguez F, Sarode R, Siegal D, Wiggins BS | title = 2017 ACC Expert Consensus Decision Pathway on Management of Bleeding in Patients on Oral Anticoagulants: A Report of the American College of Cardiology Task Force on Expert Consensus Decision Pathways | journal = Journal of the American College of Cardiology | volume = 70 | issue = 24 | pages = 3042–3067 | date = December 2017 | pmid = 29203195 | doi = 10.1016/j.jacc.2017.09.1085 | doi-access = free }}</ref> Oral vitamin K is used in situations when a person's [[International normalised ratio|International normalized ratio]] is greater than 10 but there is no active bleeding.<ref name="auto1">{{cite web|title=Important Information to Know When You Are Taking: Warfarin (Coumadin) and Vitamin K |url=http://www.cc.nih.gov/ccc/patient_education/drug_nutrient/coumadin1.pdf|publisher=[[National Institute of Health]] Clinical Center Drug-Nutrient Interaction Task Force|access-date=17 April 2015|archive-url=https://web.archive.org/web/20190405123407/https://www.cc.nih.gov/ccc/patient_education/drug_nutrient/coumadin1.pdf|archive-date=5 April 2019|url-status=dead}}</ref><ref>{{cite journal |vauthors=Wigle P, Hein B, Bernheisel CR |title=Anticoagulation: Updated Guidelines for Outpatient Management |journal=Am Fam Physician |volume=100 |issue=7 |pages=426–434 |date=October 2019 |pmid=31573167 }}</ref> The newer anticoagulants [[apixaban]], [[dabigatran]] and [[rivaroxaban]] are not vitamin K antagonists.<ref>{{cite journal |vauthors=Pengo V, Crippa L, Falanga A, Finazzi G, Marongiu F, Palareti G, Poli D, Testa S, Tiraferri E, Tosetto A, Tripodi A, Manotti C|title=Questions and answers on the use of dabigatran and perspectives on the use of other new oral anticoagulants in patients with atrial fibrillation. A consensus document of the Italian Federation of Thrombosis Centers (FCSA) |journal=Thromb. Haemost. |volume=106 |issue=5 |pages=868–876 |date=November 2011 |pmid=21946939 |doi=10.1160/TH11-05-0358 |s2cid=43611422 }}</ref>