Isoquinolinone and dihydroisoquinolinone 5-HT.sub.3 receptor antagonists

A compound of Formula I:

• ##STR22## in which:
• X and Y are independently hydrogen, halogen, hydroxy, lower alkoxy, lower alkyl, nitro, amino, aminocarbonyl, (lower alkyl)amino, di(lower alkyl)amino, or (lower alkanoyl)amino;
• R.sup.1 is hydrogen, lower alkyl, phenyl or halogen;
• R.sup.2 is a group of Formulae (a), (b), (c), or (d):
• ##STR23## in which:
• p is 0 or 1;
• q is 1, 2 or 3;
• and
• R.sup.3 is C.sub.1-7 alkyl, C.sub.3-8 cycloalkyl, C.sub.3-8 cycloalkyl-C.sub.1-2 alkyl, or a group (CH.sub.2).sub.t R.sup.4 where t is 1 or 2 and R.sup.4 is thienyl, pyrrolyl, or furyl, each optionally further substituted by one or two substituents being C.sub.1-6 alkyl, C.sub.1-6 alkoxy, trifluoromethyl or halogen, or is phenyl optionally substituted by one or two substituents being C.sub.1-4 alkoxy, trifluoromethyl, halogen, nitro, carboxy, esterified carboxy, or C.sub.1-4 alkyl optionally substituted by hydroxy, C.sub.1-4 alkoxy, carboxy, esterified carboxy or in vivo hydrolyzable acyloxy;
• and the dashed line denotes an optional bond, except that the bond is present when R.sup.1 is halogen or R.sup.2 is a group of Formula (a);
• or a pharmaceutically acceptable salt, or an individual isomer or mixtures of isomers thereof.