The invention provides compounds of the formula (I) or a pharmaceutically acceptable salt thereof, wherein R is a 5-membered ring heteroaryl group containing 3 or 4 nitrogen heteroatoms which is linked to the quinoxalinedione ring by a ring carbon or nitrogen atom said group being optionally benzo-fused and optionally substituted, including in the benzo-fused portion, by 1 or 2 substituents each independently selected from C1-C4 alkyl, C2-C4 alkenyl, C3-C7 cycloalkyl, halo, hydroxy, C1-C4 alkoxy, C3-C7 cycloalkyloxy, —COOH, C1-C4 alkoxycarbonyl, —CONR3R4, —NR3R4, —S(O)p(C1-C4 alkyl), —SO2NR3R4, aryl, aryloxy, aryl(C1-C4)alkoxy, and het, said C1-C4alkyl being optionally substituted by C3-C7 cycloalkyl, halo, hydroxy, C1-C4 alkoxy, halo(C1C4)alkoxy, C3-C7 cycloalkyloxy, C3-C7 cycloalkyl (C1-C4) alkoxy, —COOH, C1-C4 alkoxycarbonyl, —CONR3R4, —NR3R4,—S(O)p(C1-C4 alkyl), —SO2(aryl), —SO2NR3R4 morpholino, aryl, aryloxy, aryl(C1-C4)alkoxy or het, and said C2-C4 alkenyl being optionally substituted by aryl; and R1 and R2 are each independently selected from H, fluoro, chloro, bromo, C1-C4 alkyl and halo(C1-C4)alkyl. The compounds are useful as NDMA receptor antagonists for treating acute neurodegenerative and chronic neurological disorders.