Acetazolamide or dexamethasone for prevention of acute mountain sickness: a meta-analysis

Acute mountain sickness (AMS) describes a constellation of symptoms that is usually self-limited and benign. However, it may impair judgement and physical abilities at high altitudes and interfere with the pleasure of recreational activities. Severe cases may be fatal. Acclimatization is an effective prevention, but is not always practical or possible. Therefore, pharmacologic prophylaxis of AMS is an active area of research.

This study used meta-analytic techniques to evaluate the published literature regarding pharmacologic prophylaxis of AMS with acetazolamide and dexamethasone. Twenty eligible reports were located via a computer-assisted search, reference lists and review articles. Dependent measures for this study were the percentage of patients with AMS and the percentage of patients with specific symptoms associated with AMS.

An effect size (ES) is the standardized mean difference between experimental and control groups or the conversion from the point-biserial correlation between treatment and effect and allows integration of the results of independent studies. In this study, a negative ES indicates that the prophylaxis regimen exerted a protective effect; the greater the magnitude of the ES the greater its effect. The overall average weighted ES was −0.59 (95% confidence interval (CI) = −0.41 to −0.77) when both drugs’ results were pooled. The average weighted ES for studies comparing acetazolamide to placebo was −0.61 and it was −0.32 for studies comparing dexamethasone to placebo. The average ES was −0.38 when all of the reported symptoms were pooled together.

This report confirms the effectiveness of pharmacologic prophylaxis against AMS with acetazolamide or dexamethasone. Acetazolamide appears to be more effective, but inconsistencies in dexamethasone dosing, environmental conditions, and rate of ascent confound interpretation. This meta-analysis points out areas for future research.