Acetazolamide is used for prophylaxis of high-altitude sickness. Its beneficial mechanism at altitude is:

• A Inhibition of red cell carbonic anhydrase prevents CO2 transport, reducing respiratory drive and preventing hyperventilation-induced alkalosis
• B Carbonic anhydrase inhibition causes bicarbonate diuresis and metabolic acidosis, stimulating ventilation and accelerating acclimatization ✓
• C Acetazolamide directly stimulates the carotid body chemoreceptors to increase ventilation
• D Acetazolamide reduces cerebral vasodilation at altitude by inhibiting carbonic anhydrase in endothelial cells

Explanation

At high altitude, hypoxia stimulates ventilation (beneficial) but the resulting hypocapnia causes respiratory alkalosis that feeds back to inhibit further ventilation — limiting acclimatization. Acetazolamide inhibits renal carbonic anhydrase, causing bicarbonate wasting and producing a compensatory metabolic acidosis; this acidosis counteracts the respiratory alkalosis and removes the brake on ventilatory drive, allowing sustained hyperventilation and better arterial oxygenation. It also reduces CSF production, which may help with acute mountain sickness symptoms.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.