phytonadione
Brand: Mephyton, AquaMEPHYTON
Prototype Drug
Drug Class: vitamin K / warfarin reversal agent
Drug Family: reversal agent
Subclass: fat-soluble vitamin K1
Organ Systems: cardiovascularhematology-oncology
Mechanism of Action
Natural vitamin K1; provides substrate for VKORC1, restoring regeneration of vitamin K-dependent clotting factors II, VII, IX, X; reverses warfarin anticoagulation over 6-24 hours.
VKORC1 (restores function — reverses warfarin)
Indications
- warfarin reversal (supratherapeutic INR)
- vitamin K deficiency bleeding
- neonatal prophylaxis for hemorrhagic disease
Contraindications
- prior hypersensitivity reaction (IV)
Adverse Effects
Common
- injection site reactions
- flushing
- anaphylactoid reactions (IV rapid)
Serious
- anaphylaxis (rare, IV)
- resistance to warfarin re-anticoagulation for up to 2 weeks
Pharmacokinetics (ADME)
| Absorption | oral or IV/SC/IM |
| Distribution | distributes to liver |
| Metabolism | hepatic |
| Excretion | biliary and renal |
| Half-life | 1.5-3 hours |
| Onset | 6-12 hours (oral), 1-4 hours (IV) |
| Peak | 6-12 hours |
| Duration | 24-72 hours |
| Protein Binding | ~99% |
| Vd | variable |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| warfarin | reversal of anticoagulant effect | beneficial |
| cephalosporins (NMTT side chain) | vitamin K antagonism — raises INR | moderate |
Nursing Considerations
- IV preferred for major bleeding: dilute and administer over 20-60 min (not bolus — anaphylaxis risk)
- INR lowering: oral 1-2.5 mg for minor elevation; IV 5-10 mg for major bleeding
- Onset: oral 6-12 hours; IV 1-4 hours
- After large IV doses: warfarin resistance for 1-2 weeks — plan for bridging if re-anticoagulation needed
Clinical Pearls
- Restores vitamin K cycle rather than providing direct factor replacement — slower than PCC
- Warfarin resistance: large doses saturate VKORC1 for days/weeks; use lower doses when re-anticoagulation planned
Safety Profile
Pregnancy safe
Lactation generally-safe
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.