Prophylactic low-dose acetazolamide reduces the incidence and severity of acute mountain sickness

High Alt Med Biol. 2008 Winter;9(4):289-93. doi: 10.1089/ham.2008.1029.


Previous studies have shown low-dose acetazolamide to be effective in preventing AMS in persons already at high altitude and then moving higher, a relatively low risk situation. We wished to evaluate prophylactic administration of low-dose acetazolamide for reducing the incidence and severity of AMS in a high-risk setting: rapid ascent from 1600 to 4300 m. We performed a double-blind, randomized, placebo-controlled study with human subjects (n=44) exposed to 4300 m for 24 h. Subjects were treated for 3 days prior to ascent to 4300 m and during day 1 at altitude with placebo (n=22) or acetazolamide 250 mg/day (125 mg bid, n=22). AMS diagnosis required both an AMS-C score from the Environmental Symptom Questionnaire-III>or=0.7 and a Lake Louise Symptom (LLS) questionnaire score>or=3 plus headache. Acetazolamide reduced the incidence of AMS compared to placebo-treated subjects (14% vs. 45%, respectively, p=0.02), and the number needed to treat was 3. The AMS-C and LLS scores were lower in acetazolamide-treated subjects, indicating less severe AMS. Low-dose acetazolamide administered prior to ascent and on day 1 at 4300 m effectively reduced the incidence and severity of AMS in a high-risk setting.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Acetazolamide / administration & dosage*
  • Acute Disease
  • Adult
  • Altitude Sickness / drug therapy
  • Altitude Sickness / prevention & control*
  • Carbonic Anhydrase Inhibitors / administration & dosage*
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Female
  • Headache / prevention & control
  • Humans
  • Male
  • Middle Aged
  • Mountaineering*
  • Pulmonary Edema / prevention & control
  • Severity of Illness Index
  • Treatment Outcome
  • Young Adult


  • Carbonic Anhydrase Inhibitors
  • Acetazolamide