From the Guidelines
Acetazolamide is recommended at a dose of 125-250 mg twice daily to prevent altitude sickness, starting 24-48 hours before ascent and continuing for 48 hours after reaching the target altitude. For most healthy adults, 125 mg twice daily is sufficient and has fewer side effects, while those at higher risk may benefit from the 250 mg twice daily dosing 1. The medication should be taken with food to minimize gastrointestinal side effects. Acetazolamide works by causing a mild metabolic acidosis through carbonic anhydrase inhibition, which stimulates breathing and accelerates acclimatization to high altitude. This helps prevent symptoms of acute mountain sickness such as headache, nausea, fatigue, and dizziness.
Some key points to consider when using acetazolamide for altitude sickness prevention include:
- Common side effects include increased urination, tingling sensations in the extremities, and altered taste of carbonated beverages
- Acetazolamide is contraindicated in those with sulfa allergies, and should be used cautiously in people with kidney disease or electrolyte abnormalities
- While effective, acetazolamide should complement, not replace, proper acclimatization strategies like gradual ascent and adequate hydration 1
- Sex-dependent physiological reactions to hypoxia may contribute to an increased acute mountain sickness vulnerability in some women, and adequate acclimatisation, slow ascent speed and/or preventive medication (e.g. acetazolamide) are solutions 1
It's essential to note that the dose and duration of acetazolamide treatment may vary depending on individual factors, such as the altitude reached, the rate of ascent, and the presence of underlying medical conditions. Therefore, it's crucial to consult with a healthcare professional before starting acetazolamide treatment for altitude sickness prevention.
From the Research
Acetazolamide Dosing for Altitude Sickness Prevention
- The recommended dosing of acetazolamide for preventing altitude sickness varies across studies, with some suggesting doses as low as 62.5 mg twice daily 2 and others recommending higher doses of 500-750 mg/day 3.
- A study comparing 62.5 mg twice daily to the standard dose of 125 mg twice daily found the reduced dose to be noninferior in preventing acute mountain sickness (AMS) 2.
- Another study found that day of ascent dosing of acetazolamide demonstrated higher rates of AMS compared to traditional dosing, but with similar rates of severe AMS and overall symptom severity 4.
- A systematic review and meta-analysis found that acetazolamide at doses of 250 mg, 500 mg, and 750 mg daily were all effective in preventing AMS, with 250 mg daily being the lowest effective dose 5.
- The decision to use pharmacologic prophylaxis, including acetazolamide, depends on the ascent rate and an individual's previous history of altitude illness 6.
Effective Doses of Acetazolamide
- 62.5 mg twice daily: noninferior to the standard dose of 125 mg twice daily in preventing AMS 2
- 125 mg twice daily: commonly recommended dose, but may not be the most effective for rapid ascents to high altitudes 4, 3
- 250 mg daily: lowest effective dose for preventing AMS, with a number needed to treat of 6 5
- 500-750 mg/day: recommended for rapid ascents to altitudes above 3,500 m, particularly for military and emergency medical personnel 3