Protamine Injectable: Dosing and Precautions
Protamine guidance for neutralising the anticoagulant effects of heparin and enoxaparin.
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Source reviewed
August 2022
Guide category
Injectable drugs
Safety boundary
Prescription medicine information for clinician-guided use.
Kenza Health Hub presents this medicine page as structured health education. Check dose, route, interactions, pregnancy or breast-feeding considerations, and local protocol with a qualified clinician or pharmacist. Read our medical editorial policy.
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 combines source-derived medicine reference sections with Kenza editorial context, while leaving out the Storage and Remarks sections from the source batch.
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