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Acetazolamide for the Prevention of High Altitude Illness: a Comparison of Dosing

This study has been completed.
Information provided by (Responsible Party):
Scott McIntosh, University of Utah Identifier:
First received: November 12, 2013
Last updated: November 28, 2016
Last verified: November 2016

November 12, 2013
November 28, 2016
March 2012
November 2016   (final data collection date for primary outcome measure)
Prevention of acute mountain sickness as measured by the Lake Louise Score [ Time Frame: 1 year ] [ Designated as safety issue: No ]
Same as current
Complete list of historical versions of study NCT01993667 on Archive Site
Side effect profile of acetazolamide [ Time Frame: 1 year ] [ Designated as safety issue: No ]
The typical side effects of acetazolamide will be measured via a 1-5 scale: Paresthesias of fingers and toes, change in urination frequency, and change in taste of beverages.
Same as current
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Acetazolamide for the Prevention of High Altitude Illness: a Comparison of Dosing
Acetazolamide for the Prevention of High Altitude Illness: a Comparison of Dosing

Acetazolamide, or Diamox, is the standard medical prophylaxis agent for high altitude illness. The medication is effective in preventing acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE). Its mechanism is via inhibition of the carbonic anhydrase enzyme which counteracts the respiratory alkalosis which occurs during ascent to altitude. It facilitates the excretion of bicarbonate in the urine. As a result, acetazolamide hastens acclimatization and helps prevent high altitude disorders.

Current recommended dosing is 125 mg, orally twice daily, started 24 hours prior to ascending in elevation. Side effects include tingling of the fingers and toes and perioral numbness which may be erroneously interpreted as stroke symptoms. Since acetazolamide is a mild diuretic, frequent micturition may occur leading to interruption of daytime activities as well as broken sleep. These effects can affect safety at high altitude. Acetazolamide is normally discontinued 2 days after the user has reached their highest elevation or a plateau in elevation.

A lower dose may be just as effective in preventing high altitude illnesses while preventing the disconcerting side effects resulting from its use. A smaller dose has not been studied, however. We will compare the common dose of 125 mg twice daily with a lower dose of 62.5 mg twice daily.

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Phase 4
Allocation: Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Parallel Assignment
Masking: Double Blind (Subject, Investigator)
Primary Purpose: Treatment
Prophylaxis of Acute Mountain Sickness
Drug: Acetazolamide
Administration of low dose acetazolamide
Other Name: Diamox
  • Experimental: Acetazolamide normal dose
    Experimental : Acetazolamide 125 mg twice daily
    Intervention: Drug: Acetazolamide
  • Experimental: Acetazolamide low dose
    Experimental: Acetazolamide 62.5 mg twice daily
    Intervention: Drug: Acetazolamide
Not Provided

*   Includes publications given by the data provider as well as publications identified by Identifier (NCT Number) in Medline.
November 2016
November 2016   (final data collection date for primary outcome measure)

Inclusion Criteria:

  • 18 years or older
  • English or Indian speaking
  • Mountaineers or trekkers who plan to climb Mt. McKinley or trek to Base Camp on Mt. Everest

Exclusion Criteria:

  • Low sodium and/potassium blood serum levels
  • Kidney disease or dysfunction
  • Liver disease, dysfunction, or cirrhosis
  • Suprarenal gland failure or dysfunction
  • Hyperchloremic acidosis
  • Angle-closure glaucoma
  • Taking high dose aspirin (over 325 mg/day)
  • Any reaction to sulfa drugs or acetazolamide
  • Pregnant or lactating women
18 Years and older   (Adult, Senior)
Contact information is only displayed when the study is recruiting subjects
United States
Not Provided
Not Provided
Scott McIntosh, University of Utah
University of Utah
Not Provided
Principal Investigator: McIntosh Scott, MD University of Utah
University of Utah
November 2016

ICMJE     Data element required by the International Committee of Medical Journal Editors and the World Health Organization ICTRP