Pharmaceutically active compounds

摘要

Compounds of the formula (1): wherein R<1>, R<2>, R<4 >and R<13 >are as defined or a pharmaceutically or veterinarily acceptable salt or polymorph thereof, or a pharmaceutically or veterinarily acceptable solvate or pro-drug thereof: are potent and selective inhibitors of type 5 cyclic guanosine 3',5'-monophosphate phosphodiestbrase (cGMP PDE5) and have utility in the treatment of, inter alia, male erectile dysfunction (MED) and female sexual dysfunction (FSD).