Disclosed is a compound represented by formula (I) or a pharmaceutically acceptable salt thereof as an inhibitor of phosphodiesterase type 5 and its therapeutic use in treating and/or preventing a disease or condition related with phosphodiesterase type 5 in a mammal wherein an inhibition of phosphodiesterase type 5 is considered beneficial 本發明提供一種作為5型磷酸二酯酶抑制劑的通式(I)表示的化合物或其藥物可接受的鹽及其在治療及/或預防哺乳動物的與5型磷酸二酯酶相關的疾病或疾病狀態中的用途,