Along with bromantan, which we just talked about, diuretics have long served as a way to mask steroid use. A diuretic is any drug that affects kidney function, resulting in increased urine output. The "water pill" chlorthalidone, for example, prevents fluids and salts from being reabsorbed into the kidney tubules and returned to the blood. As a result, more water leaves the body. Acetazolamide works by blocking the uptake of sodium bicarbonate in the kidney tubules. Upon excretion, the bicarbonate ion carries out water, sodium and potassium.
In patients with certain conditions, such as heart disease, diuretics can help control high blood pressure and fluid retention. But athletes who take anabolic steroids pop diuretics to dilute their urine, which decreases steroid concentration and makes it much more difficult to detect. (Of course, athletes can be tested for diuretics though, too.) Weightlifters and boxers may also down water pills to expel large amounts of fluid, which qualifies them to compete in a lower weight category. Then, right before the match, they stop taking the pills to return to their heavier fighting weight, giving them an advantage against their opponents. Of course, an athlete taking diuretics may also get dizzy, become dehydrated or experience a severe drop in blood pressure -- symptoms that make it hard to fight with the eye of the tiger.