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vitamin K-1, phytonadione (Mephyton): Side Effects & Dosage

What is vitamin k-injection, and how does it work (mechanism of action)?

Phytonadione is a synthetic form of vitamin K that
is chemically identically to the naturally occurring vitamin K. Vitamin K is
found in many foods from both plant and animal sources. Common sources of
vitamin K include green leafy vegetables such as

  • broccoli,
  • Brussels sprouts,
  • collard greens,
  • lettuce, and
  • spinach.

Vitamin K plays a crucial role in blood
coagulation and the formation of blood clots. Vitamin K is necessary for the
production of clotting factors in the liver including active prothrombin
(factory II), proconvertin (factor VII), plasma thromboplastin component (factor
IX), and Stuart factor (factor X). The FDA approved phytonadione 1940.

What brand names are available for vitamin k-injection?


Is vitamin k-injection available as a generic drug?


Do I need a prescription for vitamin k-injection?


What are the side effects of vitamin k-injection?

Serious hypersensitivity reactions, including anaphylactoid
reactions and death have been reported with use of injectable phytonadione. The
majority of these cases were associated with use of intravenous phytonadione.

Other side effects reported with use of injectable phytonadione include:

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.

What is the dosage for vitamin k-injection?

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
  • 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.

Which drugs or supplements interact with vitamin k-injection?

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.

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Is vitamin k-injection safe to take if I’m pregnant or breastfeeding?

It is not known if phytonadione is excreted into human milk.
Because many drugs can enter breast milk and cause harm to the nursing infant,
phytonadione should be used cautiously in nursing mothers.

What else should I know about vitamin k-injection?

What preparations of vitamin k-injection are available?

  • Oral tablets: 5 mg, 100 mcg
  • Solution for injection: 10 mg/ml, 1 mg/0.5 ml
How should I keep vitamin k-injection stored?

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.


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