Acetazolamide (Diamox) prevents AMS when taken before ascent and can speed recovery if taken after symptoms have developed. The drug works by acidifying the blood, which causes an increase in respiration and thus aids acclimatization. An effective dose that minimizes the common side effects of increased urination and paresthesias of the fingers and toes is 125 mg every 12 hours, beginning the day before ascent and continuing the first 2 days at altitude, or longer if ascent continues. Allergic reactions to acetazolamide are uncommon, but the drug is related to sulfonamides and should not be used by sulfa-allergic persons with history of anaphylaxis. A trial dose taken in a safe environment before travel may be useful for those with a more mild allergic history to sulfonamides. People with history of severe penicillin allergy have occasionally had allergic reactions to acetazolamide.

Dexamethasone is very effective for prevention and treatment of AMS and HACE, and perhaps HAPE as well. Unlike acetazolamide, rebound can occur if the drug is discontinued at altitude prior to acclimatization. Acetazolamide is preferable to prevent AMS while ascending, with dexamethasone reserved for treatment during descent. Adult dosage is 4 mg every 6 hours.

HAPE is always associated with increased pulmonary artery pressure, and pulmonary vasodilators are useful for preventing and treating HAPE.

Nifedipine prevents and ameliorates HAPE in persons who are particularly susceptible to the condition. The adult dosage is 20 mg of extended release every 8–12 hours. PDE-5 inhibitors can also selectively lower pulmonary artery pressure, with less effect on systemic blood pressure.

Tadalafil (Cialis), 10 mg twice a day, during ascent can prevent HAPE and is being studied for treatment. When taken before ascent, gingko biloba, 100–120 mg twice daily, was shown to reduce AMS in adults in some trials, but it was not effective in others, probably due to variation in ingredients. Gingko biloba has not yet been compared directly with acetazolamide.