title: Acetazolamide reduces exercise capacity and increases leg fatigue under hypoxic conditions.
abstract: Acetazolamide (Acz) is used at altitude to prevent acute mountain sickness, but its effect on exercise capacity under hypoxic conditions is uncertain. Nine healthy men completed this double-blind, randomized, crossover study. All subjects underwent incremental exercise to exhaustion with an inspired O(2) fraction of 0.13, hypoxic ventilatory responses, and hypercapnic ventilatory responses after Acz (500 mg twice daily for 5 doses) and placebo. Maximum power of 203 +/- 38 (SD) W on Acz was less than the placebo value of 225 +/- 40 W (P < 0.01). At peak exercise, arterialized capillary pH was lower and Po(2) higher on Acz (P < 0.01). Ventilation was 118.6 +/- 20.0 l/min at the maximal power on Acz and 102.4 +/- 20.7 l/min at the same power on placebo (P < 0.02), and Borg score for leg fatigue was increased on Acz (P < 0.02), with no difference in Borg score for dyspnea. Hypercapnic ventilatory response on Acz was greater (P < 0.02), whereas hypoxic ventilatory response was unchanged. During hypoxic exercise, Acz reduced exercise capacity associated with increased perception of leg fatigue. Despite increased ventilation, dyspnea was not increased.
authors.affiliation: Department of Thoracic Medicine, Royal Brisbane Hospital, Brisbane, Queensland 4029, Australia.
authors.forename: Luke A
authors.initials: LA
authors.lastname: Garske
authors.forename: Michael G
authors.initials: MG
authors.lastname: Brown
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Morrison
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology*; D000328:Adult; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology*; D004417:Dyspnea / Q000503:physiopathology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D007866:Leg / Q000503:physiopathology*; D008297:Male; D018763:Muscle Fatigue / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D002245:Carbon Dioxide; D000086:Acetazolamide