The invention relates to compounds of formula (I) for treating for example sexual dysfunction, wherein R1 is optionally substituted C1-6alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, hydrogen, C1-6alkoxy, —NR2R3 or —NR4SO2R5; X is the linkage —(CH2)n— or —(CH2)q—O— (wherein Y is attached to the oxygen); wherein one or more hydrogen atoms in linkage X may be replaced independently by C1-4alkoxy; hydroxy; hydroxy(C1-3alkyl); C3-7cycloalkyl; carbocyclyl; heterocyclyl; or by C1-4alkyl optionally substituted by one or more fluoro or phenyl groups; n is 3, 4, 5, 6 or 7; and q is 2, 3, 4, 5 or 6; and Y is phenyl or pyridyl, each of which may be substituted; or two R8 groups on adjacent carbon atoms together with the interconnecting carbon atoms may form a fused optionally substituted 5- or 6-membered carbocyclic or heterocyclyic ring.