Paper I
2015 February (2010 Scheme) · 40 marks · 120 min

Question

Heparin.

Q73 marksShort Notes

Answer

Heparin is an injectable anticoagulant.

Mechanism of action

  • Binds to antithrombin III and enhances its activity several-fold
  • The heparin-antithrombin III complex inactivates thrombin (factor IIa) and factor Xa (and other clotting factors), preventing fibrin formation

Uses

  • Deep vein thrombosis/pulmonary embolism (treatment and prophylaxis)
  • Acute coronary syndromes, during PCI
  • During cardiopulmonary bypass/haemodialysis
  • Anticoagulant of choice in pregnancy (does not cross placenta)
  • Disseminated intravascular coagulation (early stage)

Adverse effects

  • Bleeding
  • Heparin-induced thrombocytopenia (HIT) — immune-mediated, paradoxically prothrombotic
  • Osteoporosis with prolonged use
  • Hypersensitivity reactions

Monitoring: aPTT Antidote: Protamine sulphate

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