This invention relates to novel 3-(dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-propoxybenzenesulfonamide compounds of Formula I:wherein each Y is independently selected from hydrogen and deuterium and at least one Y is deuterium, as well as to pharmaceutically acceptable salts thereof. This invention also provides compositions comprising a compound of this invention and the use of such compositions in methods of treating diseases and conditions that are beneficially treated by administering inhibitors of cyclic guanosine 3′,5′-monophosphate specific phosphodiesterase (cGMP-specific PDE), in particular PDE5.