What is the optimal way to prescribe Acetazolamide (Diamox) to prevent acute mountain sickness?

From the Guidelines

The optimal way to prescribe Acetazolamide (Diamox) to prevent acute mountain sickness is 125mg twice daily, starting 24-48 hours before ascent and continuing for 48 hours after reaching the highest altitude, while being aware of potential side effects and taking proper corrective measures. When considering the prevention of acute mountain sickness, it is crucial to weigh the benefits of prophylactic medications like acetazolamide against potential side effects, such as a transient myopic shift, as noted in a recent study 1. Key considerations for prescribing Diamox include:

• Starting dose: 125mg twice daily, with the possibility of increasing to 250mg twice daily for those with a history of altitude sickness or rapid ascent above 3000 meters.
• Timing: Initiation 24-48 hours before ascent and continuation for 48 hours after reaching the highest altitude.
• Administration: Taking the medication with food to minimize side effects.
• Patient advice: Staying well-hydrated due to the diuretic effect of Diamox.
• Contraindications and precautions: Avoidance in patients with sulfa allergies and cautious use in those with kidney disease or liver dysfunction. The mechanism of Diamox in preventing acute mountain sickness involves inducing a mild metabolic acidosis, which stimulates breathing and accelerates acclimatization to high altitude, thereby reducing the risk of symptoms such as headache, nausea, fatigue, and dizziness, as supported by the principles of managing high altitude-related conditions 1. Additionally, non-pharmacological strategies such as gradual ascent, proper hydration, and avoiding alcohol and smoking remain essential components of prevention, even when acetazolamide is used, highlighting the importance of a comprehensive approach to preventing acute mountain sickness 1.

From the Research

Optimal Prescription of Acetazolamide for Preventing Acute Mountain Sickness

• The optimal dosage of Acetazolamide for preventing acute mountain sickness is still a topic of debate, with different studies suggesting varying dosages 2, 3, 4, 5, 6.
• A study published in 2019 found that day of ascent dosing of Acetazolamide demonstrated higher rates of acute mountain sickness compared to traditional dosing, but with similar rates of severe acute mountain sickness and overall symptom severity 2.
• Another study published in 2014 recommended a dosage of 2 × 250 mg of Acetazolamide for preventing acute mountain sickness, while also highlighting the importance of slow adaptation to altitude (acclimatization) 3.
• A 2019 study compared the efficacy of 62.5 mg and 125 mg of Acetazolamide twice daily and found that the reduced dose was noninferior to the standard dose for preventing acute mountain sickness, although the study had limitations due to low incidence of acute mountain sickness in the population 4.
• However, a 2020 study found that Acetazolamide 62.5 mg twice daily failed to demonstrate equal effectiveness to 125 mg twice daily for preventing acute mountain sickness, with increased risk and no demonstrable symptomatic or physiologic benefits 5.
• An earlier study published in 1981 found that Acetazolamide was an effective prophylactic for acute mountain sickness, with a significant reduction in symptom scores compared to placebo 6.

Key Considerations

• The dosage and timing of Acetazolamide administration may impact its effectiveness in preventing acute mountain sickness 2, 4, 5.
• Acclimatization to altitude is also an important factor in preventing acute mountain sickness, and slow ascent is recommended 3.
• The efficacy and safety of Acetazolamide may vary depending on individual factors, such as weight and body mass index 5.