What is the best prescription for treating acute mountain sickness (AMS)?

Best Prescription for Altitude Sickness

Acetazolamide is the first-line prescription medication for prevention and treatment of acute mountain sickness (AMS), with a recommended dosage of 125mg twice daily starting 24 hours before ascent. 1

Pathophysiology and Clinical Presentation

Acute mountain sickness occurs due to hypobaric hypoxia at high altitudes (typically above 2,500m), causing:

• Headache (primary symptom)
• Insomnia, anorexia, nausea, dizziness
• In severe cases: vomiting, dyspnea, muscle weakness, peripheral edema

If untreated, AMS can progress to life-threatening conditions:

• High-altitude pulmonary edema (HAPE)
• High-altitude cerebral edema (HACE)

Prevention of Acute Mountain Sickness

Non-pharmacological Prevention

• Slow ascent (<400m/day above 2,500m) is the most effective prevention 1
• Rest day for every 600-1,200m gained
• Maintain adequate hydration
• High-carbohydrate, low-fat, low-salt diet
• Pre-acclimatization for 2 weeks if possible

Pharmacological Prevention

1. Acetazolamide (First-line):

   • Dosage: 125mg twice daily 1
   • Timing: Start 24 hours before ascent
   • Mechanism: Carbonic anhydrase inhibitor that increases ventilation and reduces AMS symptoms
   • Evidence shows it's effective in reducing AMS incidence and severity 2, 3
   • Higher doses (500-750mg/day) may be more effective for rapid ascents above 3,500m 3

2. Special Considerations:

   • Women may have higher risk of AMS; consider timing altitude exposure during luteal phase of menstrual cycle 1
   • Patients with cardiovascular conditions should consult their physician for medication adjustments 4

Treatment of Established AMS

For mild to moderate AMS:

• Halt further ascent
• Rest and acclimatize
• Acetazolamide 125-250mg twice daily
• Adequate hydration

For severe AMS or progression to HAPE/HACE:

1. Immediate descent (minimum 300m) - most effective treatment 1
2. Supplemental oxygen to maintain SpO₂ >90%
3. Dexamethasone for cerebral symptoms (8mg initially, then 4mg every 6 hours) 1
4. Nifedipine (20mg three times daily) specifically for HAPE when descent is impossible 4, 1
5. Portable hyperbaric chambers if descent is not possible and oxygen unavailable

Medication-Specific Considerations

Acetazolamide

• Benefits: Reduces risk of subendocardial ischemia at high altitude 1
• Side effects: Paresthesias, polyuria, altered taste of carbonated beverages
• Caution: Avoid combining with other diuretics due to increased dehydration risk 1
• Contraindications: Sulfa allergy, severe hepatic or renal insufficiency

Dexamethasone

• Effective for treating cerebral symptoms of AMS
• Not recommended for routine prophylaxis 5
• Used primarily for treatment rather than prevention

Nifedipine

• Specifically for HAPE prevention in susceptible individuals
• Dosage: 20mg three times daily, starting one day before ascent 6
• Alternative options: PDE5 inhibitors (sildenafil, tadalafil) 1

Special Populations

Cardiovascular Patients

• Well-controlled hypertensive patients may reach altitudes >4000m with adequate medical therapy 4
• Uncontrolled/severe hypertensive patients should avoid high altitude exposure 4
• Patients with NYHA class I-II can generally travel to intermediate altitudes (~2,000m) safely 1

Children

• Should follow adult prevention protocols if history of HAPE 1
• Watch for symptoms including cough, exertional dyspnea, and reduced exercise performance

Conclusion

When prescribing for altitude sickness, acetazolamide remains the gold standard medication for both prevention and treatment. For optimal results, combine pharmacological intervention with proper acclimatization strategies. In cases of severe symptoms or progression to HAPE/HACE, immediate descent is crucial along with appropriate medication.