Acetazolamide prevents acute mountain sickness (AMS) by a mechanism that involves:
- A Reduction of cerebrospinal fluid production, preventing the cerebral edema component of AMS
- B Beta-2 receptor stimulation increasing pulmonary surfactant production to prevent high-altitude pulmonary edema
- C Carbonic anhydrase inhibition in red blood cells causing CO2 retention that stimulates deeper breathing, but the main AMS prevention effect is via renal bicarbonate wasting producing a metabolic acidosis that drives ventilatory acclimatization ✓
- D Direct inhibition of HIF-1alpha hydroxylation, reducing the exaggerated hypoxic ventilatory response that causes AMS
Explanation
Acetazolamide prevents AMS primarily through renal carbonic anhydrase inhibition. By inhibiting CA in proximal tubules, it causes bicarbonaturia — the kidneys excrete HCO3-, creating a metabolic acidosis. This acidosis stimulates the carotid body chemoreceptors to increase ventilatory drive, mimicking the metabolic acidosis that normally develops over 2–3 days of acclimatization, but doing so within hours of drug administration. The resulting hyperventilation increases alveolar PO2, improving oxygenation at altitude. Additionally, CA inhibition in red blood cells slows CO2-to-bicarbonate conversion in tissues, and in the choroid plexus reduces CSF production (relevant in cerebral edema component of HACE). Acetazolamide does not stimulate beta-2 receptors.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.