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Vitamin K (clotting factor cofactor) Pregnancy: Safe — used for warfarin reversal in pregnancy; neonatal prophylaxis essential.

Phytomenadione (Vitamin K1)

Brand names: Konakion MM, Konakion MM Paediatric

Adult dose

Dose: Warfarin reversal (non-urgent): 1–5 mg oral; urgent/major bleeding: 5–10 mg IV slow infusion
Route: Oral, IV (slow — over 20 min), or IM (avoid IM in anticoagulated)
Frequency: Single dose; may repeat after 24 hours for oral
Max: 10 mg
INR 4–6 (no bleeding): 1–2 mg oral. INR >6 (no/minor bleeding): 2–5 mg oral. Major bleeding: 5–10 mg IV with PCC 4-factor. Vitamin K deficiency in newborn: 1 mg IM at birth. Hepatic disease: oral more reliable than IM.

Paediatric dose

Route: IM or oral
Frequency: Single doses as per indication
Max: 1 mg IM (neonate prophylaxis)
Concentration: 2 mg/ml
Neonatal prophylaxis: 1 mg IM at birth (preferred) or 3 doses oral (1 mg at birth, 4–7 days, 1 month — breastfed infants). VKD bleeding: 0.3 mg/kg IV slowly. Refer to BNFc for dosing by weight.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

Partial effectiveness in liver disease (synthetic function impaired regardless of Vitamin K).

Clinical pearls

  • Onset of INR correction: IV 6–8 hours; oral 12–24 hours
  • For urgent reversal, always combine with 4-factor PCC (Beriplex) — Vitamin K alone too slow
  • Small doses (1 mg) avoid overcorrection in patients needing ongoing anticoagulation
  • IM route avoided in anticoagulated patients (haematoma risk)
  • Konakion MM Paediatric (2 mg/0.2 mL) licensed for neonates

Contraindications

  • Hypersensitivity to phytomenadione

Side effects

  • Anaphylaxis (IV rapid injection — use slow infusion)
  • Flushing and dyspnoea (IV)
  • Resistance to anticoagulation (subsequent warfarin more difficult to re-dose)

Interactions

  • Warfarin — antagonises anticoagulant effect
  • Antibiotics that kill gut flora — may reduce Vitamin K synthesis (prolonged broad-spectrum use)

Monitoring

  • INR (6–8 hours after IV dose)
  • Bleeding symptoms

Reference: BNFc; BNF; BCSH 2011 Guidelines; NICE NG196. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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