Use of a compound of formula (I), or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for use in the activation of soluble guanylate cyclase, wherein: R1 and R2 are the same or different and each represent a C1-C6 alkyl group, or R1 and R2 together form a C3-C6 alkylene group; Z is a C1-C4 alkylene group; P is a direct bond or a moiety -X-, -Y-, -W-, -XY-, -YW- or -XYW-, wherein; W is -O-, -S-, or -NR3, wherein R3 is hydrogen or C1-C6 alkyl; Y is a moiety -U-V- wherein V is a direct bond or a C1-C6 alkylene group and U is -CS-, -CO-, -S(O)2- or -C(=NR)- wherein R is hydrogen, hydroxy or C1-C6 alkyl; X is -O- or -NR6- wherein R6 is hydrogen, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, aryl or heteroaryl; and R4 is C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, aryl, heteroaryl, carbocyclyl, heterocyclyl, a group -R-A wherein R is -(C1-C6 alkyl)-, -(C2-C6 alkenyl)- or -(C2-C6 alkynyl)- and A is aryl, heteroaryl, carbocyclyl or heterocyclyl, or R4 is a group -COR', -CO2R', -S(O)2R' or -CONR'R' wherein R' is hydrogen, C1-C6 alkyl, C2-C6 alkenyl or C2-C6 alkynyl and R' is aryl, heteroaryl, carbocyclyl or heterocyclyl.