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

Studies in rats have shown that the polysynaptic flexor reflex (FR) but not the monosynaptic reflexes are affected by N-methyl-D-aspartate (NMDA) receptor antagonists. Theoretically, the suppression of FR might be caused by an alteration of the spinal nociceptive neurons. To investigate, whether the non-competitive NMDA receptor antagonist memantine interferes with nociception 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 placebo or memantine (30 mg p.o.) treatment. H-reflex (HR) and FR as well as pain and tolerance threshold were determined prior to and 6 h after drug intake. Contrary to expectations, there were no differential treatment effects either on FR threshold and magnitude or on pain and tolerance thresholds or the HR amplitude.