Duration of Diamox (Acetazolamide) Treatment for Altitude Sickness
For altitude sickness prevention, acetazolamide should be started 1-3 days before ascent and continued for 2-3 days after reaching your target altitude, then discontinued.
Prophylactic Dosing Timeline
Pre-Ascent Initiation
- Start acetazolamide the night before or 1-3 days prior to ascent at a dose of 125 mg twice daily or 250 mg twice daily 1, 2, 3
- Starting the night before ascent is the traditional approach and shows slightly better efficacy than same-day dosing, though day-of-ascent dosing may be acceptable for convenience 4
- The 3-day pre-treatment period has been validated in high-risk rapid ascent scenarios 3
Duration at Altitude
- Continue acetazolamide for 2-3 days after arrival at your terminal (highest) altitude 1, 2
- This allows adequate time for physiological acclimatization to occur 2
- For staged ascents with multiple altitude gains, continue throughout the ascent period plus 2-3 days at final altitude 1
Total Treatment Duration
- Typical total duration: 3-6 days (1-3 days pre-ascent + 2-3 days at altitude) 2, 3
- Dexamethasone, if used as an alternative, should never be used for more than 2-3 days due to side effect concerns 2
Special Circumstances
High-Altitude Pulmonary Edema (HAPE) Prevention
- For patients with prior HAPE history, nifedipine should be started with ascent and continued for 3-4 days after arrival at terminal altitude 1
- This is a longer duration than standard AMS prophylaxis due to the life-threatening nature of HAPE 1
Cardiovascular Patients
- Patients with pre-existing cardiovascular conditions should continue their regular medications throughout altitude exposure 5, 1
- Acetazolamide can be added for AMS prevention using the same 2-3 day post-arrival duration, but requires careful monitoring when combined with other diuretics due to dehydration and electrolyte imbalance risks 5
- The European Society of Cardiology notes acetazolamide may reduce subendocardial ischemia risk at high altitude 5, 1
Optimal Dosing
Standard Dose
- 125 mg twice daily is the recommended dose with the best balance of efficacy and tolerability 1, 6, 7
- Alternative: 250 mg twice daily or 500 mg once daily (slow-release formulation) 1, 2
Lower Doses Not Recommended
- Acetazolamide 62.5 mg twice daily is inadequate and increases AMS risk (number needed to harm = 9) compared to 125 mg twice daily (number needed to treat = 4.8) 6
- Doses below 125 mg twice daily should not be used despite speculation about reduced side effects 6, 7
Common Pitfalls
Premature Discontinuation
- Do not stop acetazolamide immediately upon reaching altitude - the 2-3 day continuation period is critical for acclimatization 2
- Stopping too early negates the prophylactic benefit 2
Excessive Duration
- Prolonged use beyond 2-3 days at terminal altitude is unnecessary for standard AMS prevention 2
- Extended use increases cumulative side effects (paresthesias, altered taste, polyuria) without additional benefit 5, 7
Inadequate Pre-Treatment
- Starting acetazolamide only on the day of ascent shows marginally higher AMS rates (48% vs 39%) compared to night-before dosing 4
- While day-of dosing may be acceptable for convenience, night-before or 1-3 day pre-treatment is superior 4, 3
Side Effect Considerations
- Common adverse effects include paresthesias, vertigo, and unpleasant taste, which are generally mild but dose-related 5, 7
- These effects typically resolve upon discontinuation after the 2-3 day altitude exposure period 7
- The 125 mg twice daily dose provides similar efficacy to higher doses with a more favorable side-effect profile 7