Combined opioid-NMDA antagonist therapies. What advantages do they offer for the control of pain syndromes?

The potential beneficial effect of coadministration of opiates with antagonists of the N-methyl-D-aspartate (NMDA) receptor for glutamate are discussed. There is a growing body of experimental data indicating that selective NMDA antagonists acting at various receptor sites and clinically available drugs with some affinity for the NMDA receptor potentiate the analgesic effect of opiates and may block or reduce the development of tolerance following long term opiate administration. In the majority of clinical studies addressing this issue, ketamine, which has NMDA antagonist properties, has been found to reduce the need for opiates for the treatment of severe pain conditions. Thus, the combination of clinically available NMDA antagonists with opiates may be of benefit in treating a number of painful conditions.