Objective: To determine the efficacy of acetazolamide in the treatment of patients with acute mountain sickness and the effect of the drug on pulmonary gas exchange in acute mountain sickness.

Design: A randomized, double-blind, placebocontrolled trial.

Setting: The Denali Medical Research Project highaltitude research station (4200 m) on Mt. McKinley, Alaska.

Participants: Twelve climbers attempting an ascent of Mt. McKinley (summit, 6150 m) who presented to the medical research station with acute mountain sickness.

Intervention: Climbers were randomly assigned to receive acetazolamide, 250 mg orally, or placebo at 0 (baseline) and 8 hours after inclusion in the study.

Main Outcome Measures: An assessment of acute mountain sickness using a symptom score and pulmonary gas exchange measurements was done at baseline and at 24 hours.

Main Results: After 24 hours, five of six climbers treated with acetazolamide were healthy, whereas all climbers who received placebo still had acute mountain sickness (P= 0.015). Arterial blood gas specimens were obtained from three of the six acetazolamide recipients and all of the placebo recipients. The alveolar to arterial oxygen pressure difference (PAo2-Pao2 difference) decreased slightly over 24 hours in the acetazolamide group (- 0.8 ±1.2 mm Hg) but increased in the placebo group (+ 3.3 ± 2.3 mm Hg) (P = 0.024). Acetazolamide improved Pao2 over 24 hours (+ 2.9 ± 0.8 mm Hg) when compared with placebo (- 1.3 ± 2.8 mm Hg) (P = 0.045).

Conclusion: In established cases of acute mountain sickness, treatment with acetazolamide relieves symptoms, improves arterial oxygenation, and prevents further impairment of pulmonary gas exchange.


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