Abstract: Compounds of formula (I): ##STR1## and their pharmaceutically acceptable salts, wherein R.sup.1 and R.sub.2 are each independently Cl, Br, CH.sub.3, CH.sub.2 CH.sub.3 or CF.sub.3 ; R.sup.3 is H, CH.sub.3 or CH.sub.2 CH.sub.3 ; and X is a 5-membered heterocyclic group containing up to four nitrogen atoms, attached via a nitrogen atom, the said group being optionally substituted by C.sub.1 -C.sub.6 alkyl or (CH.sub.2).sub.n NR.sup.4 R.sup.5, wherein n is an integer from 1 to 5 and R.sup.4 and R.sup.5 are each independently H, C.sub.1 -C.sub.6 alkyl, C.sub.3 -C.sub.6 cycloalkyl or C.sub.1 -C.sub.4 alkyl substituted by phenyl or pyridyl, or R.sup.4 and R.sup.5 are linked to form, together with the nitrogen atom to which attached, a pyrrolidine, piperidine, piperazine, N-(C.sub.1 -C.sub.4 alkyl) piperazine, morpholine or azepine group, or, when X is triazolyl, said group may optionally be benzofused, are NMDA antagonists of value in the treatment of acute neurodegenerative disorders, e.g.