A Cochrane review [Abstract] 2 included 64 studies with a total of 4547 subjects. The risk of acute mountain sickness (AMS) was reduced with acetazolamide (table T1). Few studies reported side effects for this comparison, and they showed an increase in the risk of paraesthesia with the intake of acetazolamide. For dexamethasone, there was a trend towards reduced acute mountain sickness, but it was insignificant.
| Outcome | Relative effect (95% CI) | Assumed risk - Placebo | Risk with intervention - Acetazolamide | No of Participants (studies) |
|---|---|---|---|---|
| Incidence of acute mountain sickness | RR 0.47 (0.39 to 0.56) | 241 per 1000 | 113 per 1000 (94 to 135) | 2301 (16) |
| Incidence of high altitude pulmonary oedema (HAPE) | Not estimable | No events | 1138 (7) | |
| Incidence of high altitude cerebral oedema (HACE) | RR 0.32 (0.01 to 7.48) | 2 per 1000 | 1 per 1000 (0 to 14) | 1126 (6) |
| Outcome | Relative effect (95% CI) | Assumed risk - Placebo | Risk with intervention - Dexamethasone | No of Participants (studies) |
| Incidence of acute mountain sickness | RR 0.6 (0.36 to 1) | 449 per 1000 | 270 per 1000 (162 to 449) | 176 (4) |
A topic in Clinical Evidence 1 summarizes the results of one systematic review (search date 1999, 8 RCTs, 161 people) and three subsequent RCTs. According to the systematic review, acetazolamide 8, 12 or 16 mg daily increased the proportion of people who remained free of acute mountain sickness at altitudes above 4000 meters compared to placebo (AR 62% vs 26%, RR 2.50, 95% CI 1.71 to 3.66). Two RCTs (n=73 and 50) assessed dexamethasone 4 mg every 6 hours for a total of 6 doses) at altitudes below 4000 meters: one found dexamethasone more effective than placebo, the other did not. The third subsequent RCT (10 men in the dexamethasone arm) found that dexamethasone 0.5 mg daily vs placebo reduced the mean acute altitude sickness score after 2 days at the altitude of 3450 meters compared with placebo (p<0.001). Depression and other adverse effects on withdrawal were more common with dexamethasone than with placebo (27% with dexamethasone vs 0% with placebo). There were no RCTs of sufficient quality comparing acetazolamide and dexamethasone.
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