Sixteen percent took acetazolamide preventively (median dose 250 mg/d or 3 mg/kg/d, range 1–7 mg/kg/d) for a median of 4 days (range

1–21 d). Those who took acetazolamide preventively spent the same number of nights between 1,500 and 2,500 m, but their mean-maximum overnight altitude was slightly higher than of those who did not take it preventively: 4,178 m versus 3,917 m (p = 0.000). Five hundred and thirty-one (74%) travelers find more had physical complaints on the first days at or above 2,500 m: headache (47%), shortness of breath (44%), fatigue (23%), nausea/vomiting (14%), sleeping disorders (14%), and dizziness (4%). Other complaints included diarrhea, epistaxis, palpitations, and edema of the fingers. One person was “talking Z-VAD-FMK ic50 nonsense” for 20 minutes without any other complaint. Seven individuals had tingling sensations, six of whom took acetazolamide as prevention or treatment. One hundred and eighty-four responders (25%) had complaints that met the definition of AMS. Most (76%) of these complaints disappeared within 3 days. Some travelers with AMS adapted their travel schedule, while about half of them climbed higher despite symptoms (Table

2). Of the latter a quarter experienced worsening of symptoms. Of those who did not climb higher with symptoms, 64% were free from symptoms within 2 days, compared with 48% for those who continued to climb, but the difference was not significant (p = 0.655). The majority took medication, mostly analgesics, followed by acetazolamide and coca-leaves or -tablets. Thirty-four percent took acetazolamide for treatment at a median dose of 375 mg/d or 5 mg/kg/d (range 1–11 mg/kg/d) and a median duration of 3 days (range 1–15 d). Several travelers remarked that they did not know when to start taking acetazolamide exactly and that traveling companions had received different advice on its use. Four travelers received oxygen; all reported dyspnoea but only one met the AMS criteria. Those who did not take any medication often argued Mannose-binding protein-associated serine protease that their symptoms

were not severe enough to start acetazolamide. Those who took coca preparations often remarked that the guides had recommended coca or “soroche-pills” over acetazolamide. The majority climbed higher after the AMS symptoms disappeared; 26% of them reported that the AMS symptoms recurred. In univariate analysis, previous AMS (p = 0.014), gender (p = 0.030), age (p = 0.037), maximum overnight altitude (p = 0.015), average altitude increase in meter per day above 2,500 (p = 0.046), and number of nights between 1,500 and 2,500 m at the beginning of the journey (p = 0.000) were associated with the development of AMS (Table 3). There was no association between AMS and destination (p = 0.