This is the most tried and tested drug for altitude sickness prevention and treatment. Unlike dexamethasone (below) this drug does not mask the symptoms but actually treats the problem. It seems to works by increasing the amount of alkali (bicarbonate) excreted in the urine, making the blood more acidic. Acidifying the blood drives the ventilation, which is the cornerstone of acclimatisation.
For prevention, 125 to 250mg twice daily starting one or two days before and continuing for three days once the highest altitude is reached, is effective. Blood concentration of acetazolamide peaks between one and four hours after administration of the tablets.
Studies have shown that prophylactic administration of acetazolamide at a dose of 250mg every eight to twelve hours before and during rapid ascent to altitude results in fewer and/or less severe symptoms (such as headache, nausea, shortness of breath, dizziness, drowsiness, and fatigue) of acute mountain sickness (AMS). Pulmonary function is greater both in subjects with mild AMS and asymptomatic subjects. The treated climbers also had less difficulty in sleeping.
Gradual ascent is always desirable to try to avoid acute mountain sickness but if rapid ascent is undertaken and actazolamide is used, it should be noted that such use does not cut out the need for a prompt descent if severe forms of high altitude sickness occur, i.e. pulmonary or cerebral oedema.
Side effects of acetazolamide include: an uncomfortable tingling of the fingers, toes and face carbonated drinks tasting flat; excessive urination; and rarely, blurring of vision.
On most treks, gradual ascent is possible and prophylaxis tends to be discouraged. If trekkers develop headache and nausea or the other symptoms of AMS then treatment with acetazolamide is fine. The treatment dosage is 250 mg twice a day for about three days.
A trial course is recommended before going to a remote location where a severe allergic reaction could prove difficult to treat if it occurred.
Dexamethasone (a steroid) is a drug that decreases brain and other swelling reversing the effects of AMS. The dose is typically 4 mg twice a day for a few days starting with the ascent. This prevents most of the symptoms of altitude illness from developing.
WARNING: Dexamethasone is a powerful drug and should be used with caution and only on the advice of a physician and should only be used to aid acclimatisation by sufficiently qualified persons or those with the necessary experience of its use.
For further information go to the Mountain Medicines page...