The present invention provides a benzazepine compound that can maintain for a long period of time the blood level of tolvaptan enabling to provide the desired pharmaceutical effects. The benzazepine compound of the present invention is represented by general formula (1) wherein R1 represents a -CO-(CH2)n-COR2 group (wherein n is an integer of 1 to 4, and R2 is (2-1) a hydroxy group

The present invention provides a benzazepine compound that can maintain for a long period of time the blood level of tolvaptan enabling to provide the desired pharmaceutical effects. The benzazepine compound of the present invention is represented by general formula (1) wherein R1 represents a -CO-(CH2)n-COR2 group (wherein n is an integer of 1 to 4, and R2 is (2-1) a hydroxy group

An object of the present invention is to provide a combination drug that has remarkably excellent preventive and/or therapeutic effects on polycystic kidney disease. The present invention provides a drug for preventing and/or treating polycystic kidney disease comprising a combination of tolvaptan or a prodrug thereof with a somatostatin derivative, and a method for treating polycystic kidney disease using this drug.