26 Carlsten showed a protective effect of 250 mg bid but not of 125 mg bid in La Paz (3,630 m) in travelers who flew in from Miami (sea level).27 It is possible that a low dose of acetazolamide works better in partially acclimatized travelers at very high altitude than in travelers who just arrived at high altitude. Although most experts today advise a preventive dose of 125 mg twice daily, a review on efficacy of pharmacological prevention of AMS (which is not generally accepted) concluded that a daily dose of 500 mg acetazolamide was not effective while 750 mg was; and in his 2008

review, Wright concluded that 500 mg/d should be used preventively.28,29 The fact that we found no association between acetazolamide treatment and the duration of AMS may be because of the low average dose of 375 mg/d or 5 mg/kg/d that was taken, as the only (small) randomized controlled trial on efficacy of Selleckchem A 769662 acetazolamide treatment used 500 mg/d, which corresponds to 7 mg/kg/d for a 70 kg person.30 It could also be explained by a difference in severity of complaints in both groups, as those who did not take acetazolamide often reported that they refrained from the treatment because the symptoms were mild. This indicates a serious bias and it implies that no conclusion regarding the effect of acetazolamide treatment on the duration of symptoms can be made. This survey has several possible weaknesses. It relies on the accuracy of

self-reported data Mitomycin C collected a few weeks after return and the assumption that the responders are representative of the target population. Sclareol The response rate was higher than in several other surveys on AMS4 and of the returned questionnaires, very few had missing data. We did not phone non-responders, but several of them informed us that they ended up not climbing above 2,000 m. In this study, we did not differentiate between mild and serious complaints, which implies that we cannot conclude anything on the effect of acetazolamide treatment on the duration of AMS complaints. Of course, our study is not randomized

double-blind placebo controlled, but even in the subgroup of travelers with previous AMS we found no relation between acetazolamide prevention and AMS incidence while there was no difference in risk factors like sex, age, maximum altitude, and nights of acclimatization in those who took prevention and those who did not. As most other predictors of AMS are fixed when clients come to our travel clinic, we should stress the importance of at least 2 days of acclimatization between 1,500 and 2,500 m. As Alan J. Magill explained in the Expert Opinion Series of the International Society of Travel Medicine, even those who fly to an airport at high altitude often can descend after arrival to spend a few nights at a lower altitude.31 We should also stress the importance of a flexible travel itinerary in order to be able to change it when problems arise.