Adjuvant treatment with the NMDA receptor antagonist ifenprodil provides adequate analgesia with fewer adverse effects for cancer pain treatment

A case is presented of a 58-year-old female with bone pain from metastatic breast cancer which was poorly controlled with long-acting oxycodone. Combination treatment with ketamine was attempted and provided good analgesia, but produced psychotomimetic effects including hallucinations. Ifenprodil was therefore administered and produced good analgesia without notable adverse effects. We have previously investigated the discriminative stimulus effect induced by ketamine and have shown that non-competitive antagonists for both NR2A- and NR2B-containing NMDA receptors, such as phencyclidine and dizocilpine, and the NR2A-containing NMDA receptor-preferred antagonist dextromethorphan fully substituted for the ketamine cue in a dose-dependent manner. By contrast, the NR2B-containing NMDA. receptor antagonist ifenprodil exhibited no generalization. In conclusion, ifenprodil might be beneficial for the treatment of cancer pain with fewer adverse effects.