Abstract
To the Editor:
We thank Dr. Bennett 1 for his interest in our publication of the RADICAL (Reduced Acetazolamide Dosing in Countering Altitude Illness) trial. 2 This trial was the first to examine a dose of acetazolamide lower than the 125 mg twice daily typically recommended to prevent acute mountain sickness (AMS). During our treks and climbs in the Himalaya, we encountered guides on Mount Everest who were taking acetazolamide 62.5 mg instead of 125 mg because they believed that these smaller doses were just as effective without the side effects. We sought to rigidly examine this anecdotal use in a prospective double-blind randomized trial.
Past studies that have examined acetazolamide for preventing AMS have started acetazolamide while already at altitude, even as high as 3000 m. Our study was the first to use methods of acetazolamide administration that parallel real-life use. Participants took their first dose of acetazolamide while they were in Kathmandu (1400 m) and continued during their climb or trek. Because no published studies used these exact methods, we necessarily calculated sample sizes based on the best available information. We stand by our calculations and recognize that using a study to determine sample size that does not precisely match the population, elevation, latitude, and ascent rate has limitations. Indeed, these studies do not exist.
We agree that education in Nepal has likely decreased rates of AMS, high altitude pulmonary edema, and high altitude cerebral edema. However, trekkers and climbers in the Himalaya still succumb to AMS and other altitude illnesses at a higher rate than would be expected with this additional education. The high altitude research community does not have good data on the current rate of these altitude maladies, and this topic would serve as an excellent future project.
We agree with Dr. Bennett that a single study does not provide evidence to change practice. We have taken the first step to further explore alternate dosing regimens. We encourage Dr. Bennett and other high altitude scholars to join our efforts and design and execute additional studies to help elucidate the optimal dose of acetazolamide to prevent AMS.