Medical Editor: John P. Cunha, DO, FACOEP Last updated on RxList: 5/13/2022
Mephyton Side Effects Center

What Is Mephyton?

Mephyton (phytonadione) is a man-made form of vitamin K used to treat vitamin K deficiency and to treat certain bleeding or blood clotting problems. Mephyton usually has very few side effects.

What Are Side Effects of Mephyton?

Side effects of Mephyton include:

  • flushing (warmth, redness, or tingly feeling),
  • changes in your sense of taste,
  • sweating, or
  • dizziness.

Tell your doctor if you have serious side effects of Mephyton including:

  • feeling like you might pass out,
  • blue colored lips, or
  • trouble breathing.

Dosage for Mephyton

To correct excessively prolonged prothrombin times caused by oral anticoagulant therapy the recommended initial adult dose of Mephyton is 2.5 to 10 mg or up to 25 mg. The recommended initial adult dose to treat hypoprothrombinemia due to other causes is 2.5 to 25 mg or more (rarely up to 50 mg).

What Drugs, Substances, or Supplements Interact with Mephyton?

Mephyton may interact with warfarin, mineral oil, orlistat, cholestyramine, aspirin and other salicylates, nonsteroidal anti-inflammatory drugs (NSAIDs), or antibiotics. Tell your doctor all medications you use.

Mephyton During Pregnancy or Breastfeeding

During pregnancy, Mephyton should be used only when prescribed. It is unknown if this medication passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our Mephyton (phytonadione) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Mephyton Consumer Information

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Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

A phytonadione injection may cause a serious allergic reaction. Tell your caregiver if you feel weak, tingly, light-headed, warm, itchy, or if you have a chest pain, trouble breathing, a cold sweat, or swelling in your face.

Call your doctor at once if you have:

  • unusual or unpleasant taste in your mouth;
  • a light-headed feeling, like you might pass out;
  • blue colored lips;
  • jaundice (yellowing of the skin or eyes);
  • trouble breathing;
  • weak but rapid pulse; or
  • skin redness, itching, or a hard lump where an injection was given.

Common side effects may include:

  • dizziness;
  • flushing (warmth, redness, or tingly feeling);
  • changes in your sense of taste;
  • sweating; or
  • pain or swelling where the medicine was injected.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Mephyton (Phytonadione)


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Mephyton Professional Information


The following adverse reactions associated with the use of parenteral phytonadione were identified in clinical studies or postmarketing reports. Because some of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Severe hypersensitivity reactions, including anaphylactoid reactions and deaths, have been reported following parenteral administration. The majority of these reported events occurred following intravenous administration.

Transient “flushing sensations” and “peculiar” sensations of taste have been observed with parenteral phytonadione, as well as instances of dizziness, rapid and weak pulse, profuse sweating, brief hypotension, dyspnea, and cyanosis.

Hyperbilirubinemia has been observed in the newborn following administration of parenteral phytonadione. This has occurred primarily with doses above those recommended.



Mephyton may induce temporary resistance to prothrombin-depressing anticoagulants, especially when larger doses of Mephyton are used. Should this occur, higher doses of anticoagulant therapy may be needed when resuming anticoagulant therapy, or a change in therapy to a different class of anticoagulant may be necessary (i.e., heparin sodium).

Mephyton does not affect the anticoagulant action of heparin.

Read the entire FDA prescribing information for Mephyton (Phytonadione)

© Mephyton Patient Information is supplied by Cerner Multum, Inc. and Mephyton Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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