The present invention relates to compounds of formula I: ##STR00001## wherein one of R.sup.1 and R.sup.4 is selected from the group consisting of H, and optionally substituted C.sub.1-6 alkyl, C.sub.3-7 cycloalkyl, C.sub.3-7 cycloalkyl-C.sub.1-4 alkyl, and phenyl-C.sub.1-4 alkyl; and the other of R.sup.1 and R.sup.4 is an optionally substituted C.sub.9-14 aryl group; R.sup.2 and R.sup.3 are either: (i) independently selected from H, R, R', SO.sub.2R, C(.dbd.O)R, (CH.sub.2).sub.nNR.sup.5R.sup.6, where n is from 1 to 4 and R.sup.5 and R.sup.6 are independently selected from H and R, where R is optionally substituted C.sub.1-4 alkyl, and R' is optionally substituted phenyl-C.sub.1-4 alkyl, or (ii) together with the nitrogen atom to which they are attached, form an optionally substituted C.sub.5-7 heterocyclic group; and their use as pharmaceuticals, in particular for treating conditions alleviated by the antagonism of a 5-HT.sub.2B receptor.