Protamine Sulphate

How it works

As a strongly basic protein it binds the acidic heparin molecule to form an inactive, stable salt, abolishing heparin's potentiation of antithrombin; it only partially reverses low-molecular-weight heparins.

Prescribing in practice

• Rapid injection can cause severe hypotension, bradycardia and anaphylactoid reactions, so it must be given slowly with the dose titrated to the heparin to be neutralised.
• An excess of protamine itself has an anticoagulant effect, so avoid overdosing.
• Patients exposed to protamine-containing insulins, those with fish allergy, and vasectomised or infertile men may be at higher risk of hypersensitivity.

Monitoring

Monitor blood pressure, heart rate and the activated clotting time or APTT during and after administration to confirm heparin neutralisation.

Counselling the patient

• Inform the team this is given slowly to avoid a sudden fall in blood pressure.
• Reversal of low-molecular-weight heparin is only partial and bleeding may recur.
• Report any flushing, breathlessness or feeling faint during administration.

Evidence & guidelines

Protamine is the established antidote for unfractionated heparin and provides partial reversal of low-molecular-weight heparins.