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1 May 2026Injectable drugsSource update: August 2022

Protamine injectable

Protamine guidance for neutralising the anticoagulant effects of heparin and enoxaparin.

Prescription under medical supervision
This guide page is for structured reference only and does not replace a clinician, pharmacist, or emergency review. Dose choice, route choice, interactions, and safety decisions still need professional judgment.

Therapeutic action

Neutralisation of the anticoagulant action of unfractionated heparin and partial neutralisation of low molecular weight heparin.

Indications

  • Haemorrhagic syndromes resulting from accidental heparin overdosage.
  • Partial neutralisation of the anticoagulant action of low molecular weight heparin.

Forms and strengths, route of administration

Concentration may be expressed in antiheparin units (AHU): 1000 AHU = 10 mg.

  • 50 mg protamine sulfate in 5 ml ampoule (10 mg/ml) for slow IV injection.

Dose

Heparin overdosage

  • If administered between 0 and 30 minutes after the heparin injection, 1 mg of protamine sulfate neutralises 100 units of heparin.
  • If more than 30 minutes have elapsed since the heparin injection, the protamine dose should be one half the heparin dose injected.
  • Do not administer more than 50 mg per dose.

Enoxaparin overdosage

  • If less than 8 hours since last enoxaparin dose: 1 mg per 1 mg enoxaparin.
  • If 8 to less than 12 hours since last enoxaparin dose: 0.5 mg per 1 mg enoxaparin.
  • If more than 12 hours since last enoxaparin dose: protamine may not be required.
  • Do not administer more than 50 mg per dose.

Duration

According to clinical response. Monitor coagulation parameters.

Contra-indications, adverse effects, precautions

  • May cause hypotension, bradycardia, dyspnoea, and allergic reactions, notably in diabetics treated with protamine-insulin.
  • If excessive doses are used, haemorrhage may persist or reappear because protamine sulfate itself has some anticoagulant activity.
  • Administer by very slow IV over 10 minutes to reduce risks of hypotension and bradycardia.
  • Pregnancy and breast-feeding: no contra-indication.
  • The anticoagulant effect of protamine may vary according to the origin of the heparin: follow manufacturer's recommendations.
  • Protamine sulfate may be used to neutralize the effect of heparin before surgery.

Source

MSF Essential drugs practical guidelines (January 2026)

This page reproduces the structured reference information for this batch while leaving out the Storage and Remarks sections.

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