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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

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.

Condition Intervention Phase
Prophylaxis of Acute Mountain Sickness
Drug: Acetazolamide
Phase 4

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double Blind (Participant, Investigator)
Primary Purpose: Treatment
Official Title: Acetazolamide for the Prevention of High Altitude Illness: a Comparison of Dosing

Resource links provided by NLM:

Further study details as provided by Scott McIntosh, University of Utah:

Primary Outcome Measures:
  • Prevention of acute mountain sickness as measured by the Lake Louise Score [ Time Frame: 1 year ]

Secondary Outcome Measures:
  • Side effect profile of acetazolamide [ Time Frame: 1 year ]
    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.

Enrollment: 130
Study Start Date: March 2012
Study Completion Date: November 2016
Primary Completion Date: November 2016 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: Acetazolamide normal dose
Experimental : Acetazolamide 125 mg twice daily
Drug: Acetazolamide
Administration of low dose acetazolamide
Other Name: Diamox
Experimental: Acetazolamide low dose
Experimental: Acetazolamide 62.5 mg twice daily
Drug: Acetazolamide
Administration of low dose acetazolamide
Other Name: Diamox


Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

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
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Please refer to this study by its identifier: NCT01993667

United States, Utah
University of Utah Health Sciences Center
Salt Lake City, Utah, United States, 84132
Sponsors and Collaborators
University of Utah
Principal Investigator: McIntosh Scott, MD University of Utah
  More Information

Responsible Party: Scott McIntosh, Associate Professor, University of Utah Identifier: NCT01993667     History of Changes
Other Study ID Numbers: 00050402
Study First Received: November 12, 2013
Last Updated: November 28, 2016

Additional relevant MeSH terms:
Altitude Sickness
Respiration Disorders
Respiratory Tract Diseases
Carbonic Anhydrase Inhibitors
Enzyme Inhibitors
Molecular Mechanisms of Pharmacological Action
Natriuretic Agents
Physiological Effects of Drugs processed this record on May 25, 2017