Abstract: (S)-(?)-5-hydroxy-1-methylhydantoin is useful as a drug having high safety. Since the compound of the present invention, (S)-(?)-5-hydroxy-1-methylhydantoin, rarely changes to the metabolite having high toxicity compared with the R-form and the racemate, it is preferred as an agent for renal failure especially when used for chronic renal insufficiency in a patient where toxic substances are not excreted, but are accumulated in the body due to disturbance of renal functions.

Abstract: (R)-(+)-5-hydroxy-1-methylhydantoin is an optically active substance having an excellent suppressive action of the progression of renal failure. At an administration to a model animal of renal failure, (R)-(+)-5-hydroxy-1-methylhydantoin significantly suppresses an increase of creatinine in blood as compared with the S-form and the racemate, and shows an excellent suppressive action to the progression of renal failure by improving creatinine clearance. Thus, (R)-(+)-5-hydroxy-1-methylhydantoin is useful as a highly-active agent for renal failure.