NMDA receptor antagonists as analgesics: focus on the NR2B subtype

Ifenprodil and a group of related compounds are selective antagonists of NR 2B-containing NMDA receptors. These compounds are antinociceptive in a vari ety of preclinical pain models and have a much lower side-effect profile co mpared with other NMDA receptor antagonists. It remains unclear whether the improved safety of these compounds is due to their subtype selectivity or to a unique mode of inhibition of the receptor. Human trials have so far co nfirmed the good tolerability of these subtype-selective NMDA receptor anta gonists; however, whether they are as effective as other NMDA receptor anta gonists in pain patients remains to be demonstrated.