Treatment of Acute Mountain Sickness

To the Editor.— In a recent QUESTIONS AND ANSWERS (1983;249:1770), a question was raised concerning the prophylaxis of and therapy for highaltitude headache. I believe that Dr Dalessio's reply requires clarification and amplification. Headache occurring at high altitude is the most common manifestation of a broader constellation of symptoms, termedacute mountain sickness(AMS), that may include nausea, vomiting, anorexia, lassitude, and insomnia. Acute mountain sickness is the most common form of high-altitude illness, occurring to a variable extent in many sojourners higher than 2,400 m (8,000 ft), often after vigorous exercise or sleep at high altitude. Acetazolamide, a carbonic anhydrase inhibitor, has been shown to provide effectiveprophylaxisagainst the symptoms of AMS1,2but is not of proved therapeutic benefit in established AMS. A reasonable prophylactic regimen might be 250 mg every eight hours for 32 hours before and 40 hours after ascent.1The mechanism of benefit