Objective.—To assess the effect of acetazolamide (Az) on exercise performance during early
acclimatization to altitude.
Methods.—Az (250 mg twice daily) or placebo was administered for 3 days in a double-blind,
randomized manner followed by a rapid ascent to 3459 m in the Italian Alps. Twenty healthy adults
(age range, 18–67 years) were tested at 60% of sea-level peak power output for 15 minutes on a bicycle
ergometer after 16 to 27 hours of altitude exposure. Exercise performance was measured in relation to
peripheral oxygen saturations measured from pulse oximetry (SpO2), Lake Louise acute mountain
sickness (AMS) score, and perceived difficulty.
Results.—At altitude, resting SpO2 was higher in the Az group compared with placebo (P o .001).
The highest AMS scores were in 4 of the placebo individuals with the lowest resting SpO2 (P o .05).
During the exercise test, SpO2 fell in all but 1 subject (P o .001) and was reduced more in the Az group
(P o .01). Four Az and 1 placebo subject were unable to complete the exercise test; 4 of these 5 had the
largest fall in SpO2. The perception of exercise difficulty was higher in the Az subjects compared with
those taking the placebo (P o .01). There was an age relationship with exercise limitation; 4 of the 9
older than 50 years failed to complete the test whereas only 1 of 11 younger than 50 years failed, and
there were no failures in the 6 younger than 30 years (P o .05).
Conclusions.—In this study group, and despite higher resting SpO2, Az may have compromised
exercise at 3459 m altitude during early acclimatization, particularly in older subjects.