What medications are used to treat altitude sickness?

Medications for Altitude Sickness

For prevention and treatment of altitude sickness, acetazolamide is the first-line medication, with dexamethasone and nifedipine serving as important alternatives for specific altitude-related conditions. 1

Primary Medications for Altitude Sickness

Acetazolamide

• Mechanism: Carbonic anhydrase inhibitor that increases ventilation and arterial oxygenation
• Dosing for prevention:
  • 125-250 mg twice daily
  • Start 24 hours before ascent and continue for 2-3 days at high altitude 2, 3
  • For rapid ascents to elevations >3500m (military/emergency personnel): Higher doses (500-750 mg/day) may be more effective 3
• Efficacy: Reduces AMS symptoms by 45% in unselected groups 1
• Benefits:
  • Improves arterial oxygen saturation
  • Reduces headache, nausea, vomiting, and weakness
  • Reduces peripheral edema
  • Can lower high-altitude-induced blood pressure increases by 7-10 mmHg 1

Dexamethasone

• Primary use: For prevention and treatment of high-altitude cerebral edema (HACE)
• Dosing: First-line treatment for severe/malignant forms of acute mountain sickness 4
• Benefits: Reduces AMS symptoms partly through euphoric effects 5
• Note: Alternative to acetazolamide for those with sulfa allergies

Nifedipine

• Primary use: Prevention and treatment of high-altitude pulmonary edema (HAPE)
• Mechanism: Pulmonary vasodilator that reduces pulmonary hypertension 1, 4
• Dosing: Extended-release formulation, started with ascent and continued for 3-4 days after arrival at terminal altitude 1
• Evidence: In a placebo-controlled RCT, nifedipine reduced HAPE incidence from 7/11 (placebo) to 1/10 (treated) 1

PDE5 Inhibitors

• Options: Tadalafil, sildenafil
• Use: Alternative to nifedipine for HAPE prevention
• Caution: Tadalafil has been associated with severe acute mountain sickness in some subjects 1

Treatment Algorithm

1. For prevention of AMS (standard ascent):

   • Acetazolamide 125-250 mg twice daily, starting 24 hours before ascent
   • Optimal timing: Begin at least 2 days before arrival at high altitude for better efficacy 6

2. For prevention of AMS (rapid ascent >3500m):

   • Acetazolamide 500-750 mg/day, starting within 24 hours of altitude exposure 3

3. For prevention of HAPE in susceptible individuals:

   • Nifedipine (extended-release) started with ascent and continued for 3-4 days
   • Alternatives: Tadalafil or sildenafil (with caution)

4. For treatment of established AMS:

   • Descend to lower altitude (primary treatment)
   • Supplemental oxygen
   • Acetazolamide 500 mg/day if descent not possible 4

5. For treatment of HACE:

   • Immediate descent (critical)
   • Dexamethasone (first-line medication)
   • Supplemental oxygen

6. For treatment of HAPE:

   • Immediate descent to lower altitude
   • Supplemental oxygen
   • Nifedipine

Important Clinical Considerations

• Non-pharmacological prevention: Slow ascent (300-600 m/day above 2500m) is the most effective prevention 1, 4
• Rest days: Consider a rest day for every 600-1200m gained 1
• Avoid exertion: Delay vigorous physical activity until acclimatized 1
• Contraindications: Acetazolamide may cause transient myopic shift; patients should be aware of this side effect 1
• Side effects of acetazolamide: Paresthesia, vertigo, unpleasant taste 1
• Monitoring: For patients with cardiovascular conditions, blood pressure monitoring is recommended before and during high-altitude sojourns 1

Special Populations

• Hypertensive patients: Well-controlled hypertensive patients may reach very high altitudes (>4000m) with adequate medical therapy 1
• Patients with pulmonary hypertension: Consider supplemental oxygen when exposed to altitudes >1500-2000m 1
• Children with congenital heart disease: May be more susceptible to HAPE; consider preventive measures 1

Remember that immediate descent to lower altitude is the primary and most effective treatment for all severe forms of altitude sickness, with medications serving as adjunctive therapy.