Paper I
2024 March (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Heparin

Q63 marksShort Notes

Answer

Heparin is a rapidly-acting parenteral anticoagulant.

MOA: heparinbinds and potentiates antithrombin III (up to 1000-fold) → inactivates thrombin (IIa) and factor Xa (unfractionated heparin inactivates both; low molecular weight heparins act predominantly on Xa) → prevents further clot propagation.

Uses: prophylaxis and treatment of deep vein thrombosis/pulmonary embolism, acute coronary syndrome, during surgery/cardiopulmonary bypass, pregnancy (does not cross the placenta, unlike warfarin).

Adverse effects: bleeding, heparin-induced thrombocytopenia (immune-mediated, paradoxically prothrombotic), osteoporosis with long-term use. Monitored by aPTT; protamine sulfate is the antidote (fully reverses unfractionated heparin, only partially reverses LMWH).

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