The non-competitive N-methyl-D-aspartate-antagonist memantine does not affect segmental mono- and polysynaptic reflexes in

Studies in rats have shown that the polysynaptic flexor reflex (FR) but not the monosynaptic reflexes are affected by N-methyl-D-aspartate (NMDA) rece ptor antagonists. Theoretically, the suppression of FR might be caused by a n alteration of the spinal nociceptive neurons. To investigate, whether the non-competitive NMDA receptor antagonist memantine interferes with nocicep tion in man, we studied both its effect on pain perception and on FR. In a double-blind study 14 male subjects were randomly assigned to either placeb o or memantine (30 mg p.o.) treatment. H-reflex (HR) and FR as well as gain and tolerance threshold were determined prior to and 6 h after drug intake . Contrary to expectations, there were no differential treatment effects ei ther on FR threshold and magnitude or on pain and tolerance thresholds or t he HR amplitude. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved .