vitamin K-1, phytonadione (Mephyton) (cont.)

Pharmacy Author:
Medical and Pharmacy Editor:

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).

NURSING MOTHERS: 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.

REFERENCE: FDA Prescribing Information.

Medically Reviewed by a Doctor on 6/12/2015

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