Acetazolamide in control of acute mountain sickness.

As part of a double-blind trial slow-release acetazolamide (500 mg daily) or placebo was given to 20 men ascending to 5000 m. In the 18 who attained this altitude, those on acetazolamide had fewer symptoms of acute mountain sickness (AMS) than those on placebo (p < 0.02). 10 of the men had been to 5400 m on a previous expedition. 5 of these men took acetazolamide and 5 took placebo. Those on the drug performed better than those on placebo (p < 0.005). Furthermore, the performance of the 5 men on acetazolamide during the second expedition had improved more than that of the men on placebo (p < 0.01). In the group as a whole the symptoms of AMS were negatively correlated with arterial oxygen tensions (p < 0.001) which were higher in the drug group (p < 0.001). Acetazolamide probably had its effect by causing a metabolic acidosis with a resultant increase in respiratory drive and arterial oxygen tension.