Carbonic anhydrase inhibition in the immediate therapy of acute mountain sickness

The objective was to assess the effectiveness of acetazolamide and the relative speed of response to acetazolamide and methazolamide on blood gases and symptoms of acute mountain sickness (AMS). Thirty-seven subjects suffering from AMS were given 1–1.5 g acetazolamide or 400–500 mg methazolamide in randomized, double-blind trials during three expeditions to high altitude (3200–5486 m). Both drugs improved PaO₂ by 7.7–8.0 mmHg, with a more rapid response at 3 h following methazolamide. Symptom scores improved over 24 h following both drugs, but headaches were induced in 28% of subjects. It was concluded that treatment with acetazolamide and methazolamide improves arterial oxygenation and symptoms of AMS. The differences in time of response between the two drugs were not proven to be clinically important.