vitamin K-1, phytonadione (Mephyton)

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical and Pharmacy Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Hyperbilirubinemia (high levels of bilirubin in the blood), a byproduct of red blood cell breakdown, has been reported in newborns following administration of injectable phytonadione.

PRESCRIPTION: No

GENERIC AVAILABLE: Yes

PREPARATIONS:

  • Oral tablets: 5 mg, 100 mcg
  • Solution for injection: 10 mg/ml, 1 mg/0.5 ml

STORAGE: Tablets should be stored at room temperature between 15 C and 30 C (59 F and 86 F). Injectable vitamin K should be stored in original container at controlled room temperature between 20 C and 25 C (68 F and 77 F), and should be protected from light.

DOSING:

Oral vitamin K in Adults

  • For the treatment of anticoagulant-induced prothrombin deficiency: The initial recommended dose is 2.5 mg to 10 mg or up to 25 mg by mouth (rarely 50 mg).
  • For the treatment of hypoprothrombinemia due to other causes: the initial recommended dose is 2.5 mg to 25 mg or more (rarely up to 50 mg).
  • For the treatment of bleeding or bleeding prophylaxis in patients with warfarin toxicity: Adults with INR > 10 with no significant bleeding: administer 2.5-5 mg by mouth. Hold warfarin therapy.
  • Adults with serious bleeding at any elevation of INR: administer 5-10 mg intravenously by slow infusion in combination with 4-factor prothrombin complex concentrate. Hold warfarin therapy.
  • For the treatment of hemorrhagic disease of the newborn: administer 1 mg/dose/day intramuscularly (into the muscle) or subcutaneously (into the fatty tissue). Higher doses may be required if mother has been receiving treatment with oral anticoagulants.
  • For the prevention of hemorrhagic disease of the newborn: administer 0.5-1 mg intramuscularly within 1 hour of birth.

DRUG INTERACTIONS: Phytonadione antagonizes or blocks the therapeutic benefits of warfarin (Coumadin) treatment. Warfarin inhibits vitamin K reductase, the enzyme responsible for reducing vitamin K. The reduced form of vitamin K is used by the liver to make blood clotting factors. When phytonadione is given to treat or prevent warfarin induced bleeding, a temporary resistance to warfarin may develop. Risk of resistance is higher with use of large doses of phytonadione.

PREGNANCY: Adequate and well-controlled studies of vitamin K use in pregnancy have not been conducted. As the dietary requirements of vitamin K are not different in pregnant women, supplementation of vitamin K during pregnancy is not required. Due to the lack of conclusive safety data, vitamin K should only be used during pregnancy if the potential benefits of treatment outweigh the potential risk to the mother or the fetus. Phytonadione is classified as FDA pregnancy risk category C (Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks).

Medically Reviewed by a Doctor on 6/12/2015
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