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Heparin Antidote Pregnancy: C

Protamine Sulphate

Brand names: Protamine Sulphate Injection

Adult dose

Dose: 1 mg per 100 units unfractionated heparin (max 50 mg); partial reversal for LMWH
Route: slow IV injection (max 5 mg/min)
Frequency: single dose (repeat if needed)
Max: 50 mg per dose
For LMWH: 1 mg per 1 mg enoxaparin (given <8h ago); only ~60% effective for LMWH reversal; must give slowly — anaphylaxis risk

Paediatric dose

Route: slow IV
Frequency: single dose
Max: 50 mg
Concentration: 10 mg/mL mg/unit/ml
Dose calculated from amount of heparin given; max rate 5 mg/min

Dose adjustments

Renal

No dose adjustment required

Hepatic

No dose adjustment required

Clinical pearls

  • Must give slowly — rapid injection causes cardiovascular collapse
  • Fish allergy or previous vasectomy may increase anaphylaxis risk (antibodies to sperm proteins)
  • Only partially reverses LMWH (~60%) — anti-Xa activity may persist

Contraindications

  • Previous protamine allergy
  • Fish allergy (relative CI — sourced from salmon sperm)

Side effects

  • Anaphylaxis/anaphylactoid reactions
  • Bradycardia
  • Hypotension
  • Pulmonary hypertension
  • Flushing
  • Nausea

Interactions

  • Heparin (direct antagonist)
  • LMWH (partial antagonist)

Monitoring

  • APTT (after UF heparin reversal)
  • Anti-Xa (after LMWH reversal)
  • Blood pressure, heart rate

Reference: BNFc; BNF 86; BCSH guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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