Non-steroidal analgesic and anti-inflammatory drugs (NSAID) are potent inhibitors of prostaglandin synthesis in vivo at commonly achieved concentrations of these drugs. Prostaglandins of the E-series are released by exercising muscles, and their release is inhibited by indomethacin. The consequences, with respect to exercise performance, are unknown. Drugs used for hyperuricemia and gout such as colchicine, allopurinol, probenecid, and sulphinpyrazone have not been implicated in affecting exercise performance. The uricosuric drugs probenecid and sulphinpyrazone may be contraindicated in individuals who exercise heavily because of the increased danger of precipitating uric acid crystals in the kidney tubules. Muscle relaxants do not cause measurable muscle relaxation following usual oral dosage regimens. They are, however, sedatives and this property could influence exercise performance.