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2024 June (Supplementary) (2019 Scheme) · 100 marks · 180 min

Question

Pharmacological basis for the use of Protamine sulphate in heparin overdosage.

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Answer

Protamine sulfate is a strongly basic (cationic) protein that binds ionically to strongly acidic heparin, forming a stable, inactive complex — neutralizing heparin’s anticoagulant activity within minutes of IV administration. It fully reverses unfractionated heparin (which is uniformly negatively charged and binds protamine completely) but only partially reverses low molecular weight heparin (whose shorter chains bind protamine less completely, particularly the Xa-inhibiting fraction), making it the specific antidote for heparin overdose/excessive bleeding on heparin therapy. Excess protamine itself has anticoagulant activity, so dosing is calculated against the estimated residual heparin dose rather than given in excess.

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