Efficacy and harm of pharmacological prevention of acute mountain sickness: quantitative systematic review.
OBJECTIVE
To quantify efficacy and harm of pharmacological prevention of acute mountain sickness.


METHODS
Systematic search (Medline, Embase, Cochrane Library, internet, bibliographies, authors) in any language, up to October 1999.


METHODS
Randomised placebo controlled trials.


METHODS
Dichotomous data on efficacy and harm from 33 trials (523 subjects received 13 different interventions, 519 a placebo).


RESULTS
At above 4000 m the mean incidence of acute mountain sickness with placebo was 67% (range 25% to 100%); incidence depended on the rate of ascent, but not on the altitude or the mode of ascent. Across all ascent rates, dexamethasone 8-16 mg prevented acute mountain sickness (relative risk 2.50 (95% confidence interval 1.71 to 3.66); number needed to treat (NNT) 2.8 (2.0 to 4.6)), without evidence of dose responsiveness. Acetazolamide 750 mg was also efficacious (2.18 (1.52 to 3.15); NNT 2.9 (2.0 to 5.2)), but 500 mg was not. In two trials, adverse reaction (including depression) occurred after dexamethasone was stopped abruptly (4.45 (1.08 to 18); NNT 3.7 (2.5 to 6.9)). With acetazolamide, paraesthesia (4.02 (1.71 to 9.43); NNT 3.0 (2.0 to 6.0)) and polyuria (4.24 (1.92 to 9.37); NNT 3.6 (2.5 to 6.2)) were reported. Data were sparse on nifedipine, frusemide (furosemide), dihydroxyaluminium-sodium, spironolactone, phenytoin, codeine, phenformin, antidiuretic hormone, and ginkgo biloba.


CONCLUSIONS
At above 4000 m, with a high ascent rate, fewer than three subjects need to be treated with prophylactic dexamethasone 8-16 mg or acetazolamide 750 mg for one subject not to experience acute mountain sickness who would have done so had they all received a placebo. Acetazolamide 500 mg does not work.
Division of Anaesthesiology, Department APSIC, University of Geneva Hospitals, CH-1211 Geneva 14, Switzerland. lionel.dumont@hcuge.ch
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Tramèr
D000086:Acetazolamide / Q000627:therapeutic use*; D000208:Acute Disease; D000532:Altitude Sickness / Q000517:prevention & control*; D002121:Calcium Channel Blockers / Q000627:therapeutic use; D016001:Confidence Intervals; D003907:Dexamethasone / Q000627:therapeutic use*; D004232:Diuretics / Q000627:therapeutic use*; D005938:Glucocorticoids / Q000627:therapeutic use*; D006801:Humans; D009543:Nifedipine / Q000627:therapeutic use; D016032:Randomized Controlled Trials as Topic; D012306:Risk
D002121:Calcium Channel Blockers; D004232:Diuretics; D005938:Glucocorticoids; D003907:Dexamethasone; D009543:Nifedipine; D000086:Acetazolamide