From the Guidelines
Acetazolamide should be dosed at 125-250 mg twice daily for the prevention and treatment of altitude sickness. For prevention, it is recommended to start taking it 24-48 hours before ascending to high altitude and continue for at least 48 hours after reaching your maximum altitude, or longer if symptoms persist. This dosing regimen is based on the most recent and highest quality study available, which emphasizes the importance of proper acclimatization practices, such as gradual ascent, staying hydrated, and avoiding alcohol and smoking 1.
Key Considerations
- The medication works by causing the kidneys to excrete bicarbonate, creating a mild metabolic acidosis that stimulates breathing and increases oxygen levels in the blood, thus helping acclimatization to high altitude environments.
- Common side effects include increased urination, tingling sensations in the extremities, and altered taste of carbonated beverages.
- Acetazolamide should be avoided in people with sulfa allergies, and those with kidney problems or liver disease may need dose adjustments.
- Staying well-hydrated while taking acetazolamide is important due to its diuretic effect.
Important Notes
- While acetazolamide helps with acclimatization, it doesn't replace proper acclimatization practices like gradual ascent.
- High altitude illness, including acute mountain sickness, is primarily prevented by proper acclimatization, gradual ascent, staying hydrated, and avoiding alcohol and smoking 1.
- The older study from 1992 recommends a dose of 250 mg three times a day for 5 days 1, but this is not considered the most recent or highest quality evidence for guiding current practice.
From the Research
Acetazolamide Dosing for Altitude Sickness
- The recommended dosing of acetazolamide for altitude sickness varies, with studies suggesting doses of 125,250,500, and 750 mg daily are efficacious in decreasing the incidence and/or severity of acute mountain sickness (AMS) during rapid ascents 2.
- A systematic review and meta-analysis found that acetazolamide at doses of 250 mg, 500 mg, and 750 mg daily are all effective in preventing AMS above 3000 m, with a combined odds ratio of 0.36 (95% confidence interval 0.28 to 0.46) 3.
- The lowest effective dose of acetazolamide for the prophylaxis of AMS is 250 mg daily, with a number needed to treat of 6 (95% confidence interval 5 to 11) 3.
- For military, emergency medical, or other activities involving rapid ascent to altitudes >3,500 m, doses of 500-750 mg/day within 24 hours of altitude exposure appear to be the most effective for minimizing symptoms of AMS 2.
- Acetazolamide alone was moderately beneficial in preventing the occurrence of AMS, although minor side effects were frequent, while combined drug therapy with dexamethasone was superior to both placebo and single drug therapy in risk reduction 4.
Comparison of Different Doses
- A study comparing different doses of acetazolamide found that higher doses (500-750 mg daily) were more effective in preventing AMS than lower doses (125-250 mg daily) 2.
- Another study found that acetazolamide at a dose of 250 mg daily was effective in preventing AMS, but had a higher number needed to treat compared to higher doses 3.
Clinical Guidelines
- The BMJ Clinical Evidence review recommends acetazolamide as an effective intervention for preventing and treating AMS, with a GRADE evaluation of the quality of evidence for interventions 5, 6.
- The review also notes that slow ascent, descent versus resting, and dexamethasone are other effective interventions for preventing and treating AMS, although the evidence for these interventions is not as strong as for acetazolamide 5, 6.