Compounds of formula (I): ##STR00001## wherein A is S or O; R is H; Ar is an optionally substituted phenyl group; X is an optionally substituted phenyl group, a C.sub.1-C.sub.4 alkyl, a C.sub.3-C.sub.6 cycloalkyl group or a CH.sub.2(C.sub.3-C.sub.6 cycloalkyl) group; R' is H or C.sub.1-C.sub.4 alkyl; and each R.sup.1 is independently H or C.sub.1-C.sub.4 alkyl; and pharmaceutically acceptable salts thereof are selective inhibitors of norepinephrine reuptake.