Drug interactions
Phylloquinone + Warfarin
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Phylloquinone (vitamin K1) reduces warfarin’s anticoagulant effect, lowering INR and increasing thrombosis risk; pharmacologic doses are used to reverse warfarin.
Mechanism of action
Pharmacodynamic antagonism: exogenous vitamin K1 replenishes reduced vitamin K and restores gamma-carboxylation of clotting factors II, VII, IX, and X, overcoming VKORC1 inhibition by warfarin.
Clinical management
Avoid routine vitamin K supplementation while on warfarin unless intentional reversal is needed. Maintain consistent dietary vitamin K intake. Recheck INR within 3–7 days after starting/stopping vitamin K–containing supplements or major diet changes and adjust warfarin dose per INR. For reversal, administer oral/IV vitamin K per guidelines and hold/modify warfarin.
Drug reference
References
- COUMADIN (warfarin sodium) Prescribing Information — FDA Label
- Warfarin: Drug interactions — Lexicomp
- Vitamin K and the management of warfarin-associated coagulopathy — UpToDate
Frequently asked questions
Can I take Phylloquinone with Warfarin?
The interaction is rated: Major. Phylloquinone (vitamin K1) reduces warfarin’s anticoagulant effect, lowering INR and increasing thrombosis risk; pharmacologic doses are used to reverse warfarin.
How serious is the interaction between Phylloquinone and Warfarin?
The interaction is rated: Major. Evidence level: High.
How is the interaction between Phylloquinone and Warfarin managed?
Avoid routine vitamin K supplementation while on warfarin unless intentional reversal is needed. Maintain consistent dietary vitamin K intake. Recheck INR within 3–7 days after starting/stopping vitamin K–containing supplements or major diet changes and adjust warfarin dose per INR. For reversal, administer oral/IV vitamin K per guidelines and hold/modify warfarin.
Why do Phylloquinone and Warfarin interact?
Pharmacodynamic antagonism: exogenous vitamin K1 replenishes reduced vitamin K and restores gamma-carboxylation of clotting factors II, VII, IX, and X, overcoming VKORC1 inhibition by warfarin.
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