Probenecid

Probenecid (Fig. 1) is a substance that increases the excretion of uric acid into the urine. Elevated uric acid levels can lead to a gout attack over time. Substances that increase uric acid excretion are called uricosurics.

Significance as a Doping Agent

Probenecid inhibits the renal excretion of a wide range of medications into the urine. This allows the use of other medications, such as penicillin, to be avoided.
Most banned steroid hormones are eliminated into the urine as so-called "sugar derivatives" (glucuronides: steroid conjugates with glucuronic acid), and probenecid also retains these compounds in the body longer via the same mechanism.

Consequently, only small amounts of the steroids are excreted into the urine, and analytical detection of the steroid hormones can be made more difficult or, under certain circumstances, prevented entirely. For this reason, the IOC designated the use of probenecid as a doping method to manipulate a submitted urine sample in 1987. The ban applies both during competition and outside of competition ("training phase").