What is the best medication for acute mountain sickness (AMS) or elevation sickness?

Acetazolamide is the Best Medication for Acute Mountain Sickness

Acetazolamide (125-250mg twice daily) is the most effective medication for prevention and treatment of acute mountain sickness (AMS), with strong evidence supporting its use as the primary pharmacological intervention. 1

Mechanism and Effectiveness

Acetazolamide works by:

• Acting as a carbonic anhydrase inhibitor that increases ventilation
• Reducing the risk of subendocardial ischemia at high altitude 1
• Improving oxygen saturation while simultaneously alleviating mountain sickness symptoms 2
• Providing a 48% relative risk reduction compared to placebo 3

Dosing Recommendations

The optimal dosing depends on altitude and ascent speed:

• Standard prevention: 125mg twice daily starting 24 hours before ascent 1
• Day of ascent dosing: Can be effective but may have slightly higher AMS rates compared to starting the night before 4
• Rapid ascent to >3500m: Higher doses (500-750mg/day) are more effective for military or emergency personnel 5

Alternative Medications

While acetazolamide is first-line, other medications have specific roles:

• Dexamethasone: Effective for treating cerebral symptoms of AMS but not routinely recommended for prophylaxis 6
• Nifedipine: Specifically for high-altitude pulmonary edema (HAPE) prevention in susceptible individuals (20mg three times daily) 7
• PDE5 inhibitors (sildenafil, tadalafil): Alternative options for HAPE-susceptible individuals 1

Non-Pharmacological Prevention

Medication should always be combined with these essential preventive measures:

• Slow ascent: Most effective prevention (<400m/day above 2,500m) 1
• Rest days: Include one rest day for every 600-1200m gained 1
• Pre-acclimatization: For those with access to altitude facilities, 2 weeks with >8h/day at progressively increasing altitudes 1
• Diet: High-carbohydrate, low-fat, low-salt diet helps prevent AMS 6
• Hydration: Maintain adequate fluid intake 1

Special Considerations

• Women: May have higher AMS risk; consider timing altitude exposure during luteal phase of menstrual cycle 2, 1
• Hypertensive patients: Acetazolamide lowers blood pressure at high altitude while improving oxygen saturation 2
• Combination therapy: Avoid combining acetazolamide with other diuretics to prevent dehydration 1

Common Pitfalls to Avoid

1. Inadequate dosing: Using too low a dose for rapid ascents to high altitudes
2. Delayed treatment: Waiting too long after symptoms appear to begin medication
3. Relying solely on medication: Neglecting non-pharmacological prevention strategies
4. Inappropriate medication selection: Using nifedipine for routine AMS without pulmonary symptoms
5. Continuing ascent despite symptoms: Immediate descent (minimum 300m) is critical for severe AMS 1

For severe symptoms or progression to high-altitude cerebral edema (HACE) or pulmonary edema (HAPE), immediate descent and supplemental oxygen are essential interventions that should not be delayed while waiting for medications to take effect.