What is the recommended dose and administration instructions for acetazolamide (Diamox) for a patient requiring high altitude prophylaxis (PPX)?

From the Guidelines

For high altitude illness prevention, I recommend acetazolamide 125 mg twice daily, starting 24-48 hours before ascent and continuing for 48 hours after reaching the highest altitude. This dosage is based on the most recent and practical recommendations for travel to high altitude destinations 1. The medication can be taken with or without food, but taking it with food may reduce gastrointestinal side effects. The patient should be advised that acetazolamide commonly causes tingling in the fingers and toes, altered taste sensation (particularly with carbonated beverages), and increased urination. These side effects are expected and not dangerous. The patient should stay well-hydrated while taking the medication. Acetazolamide works by causing a mild metabolic acidosis, which stimulates breathing and helps acclimatization to high altitude. Some key points to consider when prescribing acetazolamide for high altitude illness prevention include:

• The patient should be aware of potential side effects like a transient myopic shift and have proper corrective measures in place 1
• High altitude illness, including acute mountain sickness, is primarily prevented by proper acclimatization, gradual ascent, staying hydrated and avoiding alcohol and smoking 1
• The patient should still follow other altitude illness prevention strategies like gradual ascent (not increasing sleeping elevation by more than 1,500-2,000 feet per day above 8,000 feet) and avoiding alcohol during the acclimatization period. It is also important to note that acetazolamide is contraindicated in patients with sulfa allergies, severe kidney or liver disease, and certain electrolyte abnormalities. The patient should be monitored for any signs of high altitude retinopathy (HAR) or non-arteritic ischaemic optic neuropathy (NAION), which can occur in some individuals who travel to high altitudes 1.

From the Research

Acetazolamide Dosage for High Altitude Prevention

• The recommended dosage of acetazolamide for prevention of acute mountain sickness (AMS) varies, but studies suggest that 250 mg/day is effective and may have a favorable side-effect profile 2.
• Higher doses, such as 500-750 mg/day, may be more effective for minimizing symptoms of AMS during rapid ascents to altitudes >3,500 m 3.
• A dose of 125 mg twice daily has also been shown to be effective in preventing AMS, although it may not be as effective as higher doses 4.

Administration Instructions

• Acetazolamide should be started 12 to 24 hours before ascent to high altitude 5.
• The medication can be taken in the morning or at night, although some studies suggest that taking it the night before ascent may be more effective 4.
• Patients should be advised to drink plenty of water and to monitor their symptoms closely while taking acetazolamide.

Side Effects and Considerations

• Acetazolamide can cause side effects such as nausea, headaches, and fatigue, although these are generally mild 2.
• Patients with sulfa intolerance should not take acetazolamide, and alternative medications such as dexamethasone may be considered 5.
• Acetazolamide may not be effective in preventing high-altitude pulmonary edema (HAPE), and other medications such as dexamethasone, tadalafil, and nifedipine may be more effective for this condition 6.