Vitamin K — Anticoagulant Reversal / Haemostasis Pregnancy: Safe in pregnancy — essential for neonatal HDN prevention

Phytomenadione (Vitamin K1)

Brand names: Konakion MM

Adult dose

Dose: 1-10 mg IV slowly (warfarin reversal — dose guided by INR and urgency); 10 mg IV (urgent reversal)

Route: Intravenous (slow — over 20-30 min) / Oral

Frequency: Single dose; repeat at 6-8 hours if INR not adequately corrected

Max: 10 mg IV per dose

INR 5-8 without bleeding: oral 1-5 mg. INR above 8 or minor bleeding: oral/IV 5 mg. Major/life-threatening bleeding: 10 mg IV + PCC (Beriplex) — phytomenadione alone takes 4-6 hours to act

Paediatric dose

Dose: 15-25 micrograms/kg (neonatal prophylaxis: 1 mg IM at birth) mg/kg

Route: IM (neonatal) / IV / Oral

Frequency: Single or repeated doses as needed

Max: 1 mg IM (neonatal prophylaxis)

Neonatal prophylaxis: 1 mg IM at birth (all neonates — prevents haemorrhagic disease of newborn). Child: seek specialist opinion

Dose adjustments

Renal

No dose adjustment required

Hepatic

Hepatic synthesis of clotting factors may remain impaired despite vitamin K in severe liver disease — PCC or FFP may be needed

Paediatric weight-based calculator

Patient weight (kg)

Neonatal prophylaxis: 1 mg IM at birth (all neonates — prevents haemorrhagic disease of newborn). Child: seek specialist opinion

Clinical pearls

For urgent warfarin reversal (major bleeding or emergency surgery): always combine phytomenadione 10 mg IV with PCC (Beriplex/Octaplex) — PCC provides immediate factor replacement; vitamin K sustains correction by restoring factor synthesis (takes 4-6 hours)
Anaphylactoid reactions: use Konakion MM (colloidal micellar formulation) — safer than older Cremophor-containing formulations; infuse slowly over 20-30 minutes; have resuscitation available
Large doses (10 mg) cause warfarin resistance for up to 2 weeks — use minimum effective dose to preserve ability to re-anticoagulate if needed (e.g. AF); oral 1-3 mg is often sufficient for non-urgent reversal
Haemorrhagic disease of newborn (HDN) prevention: universal IM vitamin K at birth is mandatory standard of care in UK — prevents potentially fatal intracranial bleeding
Liver disease: vitamin K administration alone is insufficient when INR elevated due to hepatocellular failure — check whether INR responds to vitamin K (5 mg oral); if not, liver disease is the cause, not vitamin K deficiency

Contraindications

Rapid IV infusion (anaphylactoid reactions reported)

Side effects

Anaphylactoid reactions (IV route — related to vehicle; use Konakion MM colloidal formulation and infuse slowly)
Resistance to subsequent warfarin therapy (large doses make re-anticoagulation difficult for 1-2 weeks)
Flushing (with rapid IV)

Interactions

Warfarin (reversal agent — expected)
Broad-spectrum antibiotics (reduce vitamin K-producing gut flora — potentiate warfarin effect)

Monitoring

INR (6-8 hours after dose)
Signs of bleeding
Anaphylactoid reaction during IV infusion

Reference: BNFc; BNF 90; BSH Anticoagulant Reversal Guidelines 2022; Konakion MM SPC; BCSH Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways