Altitude Sickness Prevention Medication
Acetazolamide at a dose of 125-250 mg twice daily, starting 24 hours before ascent, is the recommended medication for preventing altitude sickness. 1
Medication Options and Dosing
Acetazolamide (First-Line)
- Standard dosing: 125-250 mg twice daily starting 24 hours before ascent 1
- Higher risk situations: 500-750 mg/day may be more effective for rapid ascents to elevations >3,500 m, particularly for military or emergency personnel 2
- Lower dose option: 62.5 mg twice daily has been shown to be noninferior to 125 mg twice daily in some studies 3
- Duration: Continue for 2-3 days at high altitude or until acclimatization occurs
Alternative Medications
- Nifedipine: 20 mg extended-release every 8 hours is recommended specifically for individuals with history of high-altitude pulmonary edema (HAPE) 1, 4
Effectiveness and Evidence
Acetazolamide reduces the risk of acute mountain sickness (AMS) by approximately 48% compared to placebo 5. The medication works by:
- Increasing ventilation
- Improving nocturnal oxygenation
- Reducing sleep apnea intensity by up to 45% at high altitude 1
Recent evidence suggests that while the traditional 125 mg twice daily dosing is effective, higher doses (500-750 mg/day) may provide enhanced protection for rapid ascents above 3,500 meters 2. However, higher doses may also increase side effects.
Administration Timing
- Traditional approach: Begin 24 hours before ascent 1
- Day-of-ascent option: Starting acetazolamide on the day of ascent showed slightly higher rates of AMS compared to night-before dosing, but similar rates of severe AMS 6
Side Effects and Precautions
- Common side effects: Paresthesias, altered taste, increased urination, dizziness, fatigue 1
- Serious side effects: Kidney stones, metabolic acidosis, lethargy, suppressed appetite 1
- Contraindications: Sulfa allergy, severe hepatic or renal disease, adrenocortical insufficiency, hyperchloremic acidosis 1
Important Considerations
- Hydration: Maintain adequate fluid intake as acetazolamide has diuretic effects
- Caffeine: Limit caffeine intake when taking acetazolamide to avoid worsening dehydration 1
- Electrolytes: Monitor for electrolyte disturbances, particularly hypokalemia 1
- Combining with other diuretics: Avoid if possible due to increased risk of dehydration 1
Non-Pharmacological Prevention
Even with medication, proper acclimatization remains essential:
- Gradual ascent (300-600 m/day above 2,500 m)
- Include rest days (one day for every 600-1,200 m gained)
- Avoid overexertion
- Maintain adequate hydration 1
Treatment of Established Altitude Sickness
If altitude sickness develops despite prophylaxis:
- Immediate descent to lower altitude is the primary treatment
- Supplemental oxygen to maintain saturation >90%
- Consider additional acetazolamide for treatment (250 mg twice daily) 1
Remember that medication is only one component of altitude sickness prevention, and proper acclimatization remains the cornerstone of prevention.