Soon after the antibacterial drug sulfanilamide appeared in the late 1930s, it was noted that even normal doses modified the acid-base balance in the body, leading to the loss of large volumes of alkaline urine. The imbalance was caused by sulfanilamide blocking carbonic anhydrase, an enzyme required for transforming carbon dioxide and water to carbonic acid in the body.
Following this discovery, the search for chemical variations of sulfa drugs that were more potent carbonic anhydrase inhibitors and more effective diuretics (increasing the outflow of urine) began. The most promising of these was acetazolamide, marketed by Lederle Laboratories in 1952 as Diamox. Diamox was never a very impressive diuretic, particularly when used alone, but happily, it was not shelved. Its chemical cousin Diuril is the first of the thiazide diuretics.
Diamox’s most important current use is for the treatment of glaucoma, one of the major causes of blindness. Glaucoma is associated with increased pressure within the eye that results from more fluids being formed inside the eye than leaving it. Diamox and related drugs, when taken by mouth or as eye drops, decrease the production of this fluid.
Diamox is the most widely used drug for the prevention and treatment of acute mountain (or altitude) sickness. Whereas there is considerable variation in our susceptibility to altitude sickness, early flu-like symptoms may occur at 8,000 feet (2,500 meters). Severe symptoms are not experienced until heights of over 12,000 feet (4,000 meters) are reached.
At 8,000 feet, the air contains 25 percent less oxygen than at sea level. This causes blood to leak from the smallest blood vessels (capillaries) into surrounding tissues. Even modest fluid buildup in the brain causes symptoms of acute mountain sickness. Diamox is thought to work by increasing the acidity of the blood, stimulating the breathing center in the medulla region of the brain, which increases ventilation, including during periods of sleep. The most effective method of preventing altitude sickness remains the gradual acclimatization to altitude when climbing.
SEE ALSO Sulfanilamide (1936), Diuril (1958).
With increasing altitude, there is a drop in atmospheric pressure and a corresponding drop in oxygen pressure. At the summit of Mount Everest (29,021 feet/ 8848 meters), the pressure of inspired oxygen is only 29 percent of that at sea level. This sign, warning of altitude sickness, is posted at Mount Evan (14,265 feet/4348 meters) in Colorado.