A Unique Case Report on Methadone Used for Treatment of Opioid-induced Hyperalgesia in a Cancer Patient at the End of Life.

Opioids are the cornerstone of palliative pain management. Opioids work on the mu-opioid receptor as an agonist for the treatment of pain. Repeated exposure to opioids over time can lead to undesired desensitization of the antinociceptive receptor while sensitizing the N-methyl-D-aspartate (NMDA) pathway, causing a paradoxical effect where the treatment of pain creates more sensitivity to certain stimuli. This phenomenon is known as opioid-induced hyperalgesia (OIH). Methadone, a synthetic opioid, may be more effective for pain and offers advantages over other opioids in specific clinical situations due to its partial antagonistic effect on the NMDA pathway. We describe a unique case where as needed (prn) and continuous intravenous (IV) methadone was effective in relieving OIH caused by high doses of IV Dilaudid for intractable cancer pain at the end of life. Given its unique pharmacokinetics, effective pain control, and the prevention of suffering from OIH, methadone should be considered earlier on in palliative pain management, especially in those patients predicted to require high levels of opioid dosing.