Abstract: There is provided compounds of formula IA and of formula IB, wherein R1, R2, R3, R4 and A have meanings given in the description, which are useful in the curative and prophylactic treatment of medical conditions for which inhibition of a cyclic guanosine 3′,5′-monophosphate phosphodiesterase (e.g. cGMP PDE5) is desired.

Abstract: Compounds of the formulae (IA) and (IB): 1

Abstract: Compounds of the formulae (IA) and (IB): wherein R1 is C1 to C3 alkyl optionally substituted with phenyl, Het or a N-linked heterocyclic group selected from piperidinyl and morpholinyl; wherein said phenyl group is optionally substituted by one or more substitutents selected from C1 to C4 alkoxy; halo; CN; CF3; OCF3 or C1 to C4 alkyl wherein said C1 to C4 alkyl group is optionally substituted by C1 to C4 haloalkyl or haloalkoxy either of which is substituted by one or more halo atoms; R2 is C1 to C6 alkyl and R13 is OR3 or NR5R6, or pharmaceutically or veterinarily acceptable salts thereof, or pharmaceutically or veterinarily acceptable solvates of either entity are potent and selective inhibitors of type 5 cyclic guanosine 3′,5′-monophosphate phosphodiesterase (cGMP PDE5) and have utility in the treatment of, inter alia, male erectile dysfunction (MED) and female sexual dysfunction (FSD).