Paper I
2014 March (2010 Scheme) · 40 marks · 120 min

Question

Sodium nitroprusside

Q33 marksShort Notes

Answer

Sodium nitroprusside is a potent, short-acting parenteral vasodilator.

Mechanism of action

  • Releases nitric oxide non-enzymatically, which activates guanylyl cyclase → increases cGMP → relaxes both arteriolar and venous smooth muscle (balanced arterial and venous dilator)

Uses

  • Hypertensive emergencies (given as IV infusion, rapid onset, easily titratable)
  • Acute severe heart failure (reduces preload and afterload)
  • Controlled hypotension during surgery

Adverse effects

  • Cyanide toxicity — nitroprusside is metabolized to cyanide, which is further converted to thiocyanate; accumulates with prolonged use or renal/hepatic impairment
  • Thiocyanate toxicity (with prolonged infusion) — tinnitus, confusion, psychosis
  • Hypotension
  • Requires protection from light (photodegradation) and continuous BP monitoring during infusion

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