A Comparative Study of Opioid Switching to Methadone for Cancer Pain Control in Successful and Unsuccessful Cases.

Background: Methadone may play a role in the control of refractory cancer pain in opioid switching, although some cases fail to switch to methadone. Objective: To evaluate the differences in the clinical aspects in switching to methadone between successful cases (SCs) and unsuccessful cases (UCs). Design: This was a retrospective study of the clinical aspects of cancer patients who experienced opioid switching from other opioids to methadone. Setting/Subjects: Eighty-seven patients who were prescribed oral methadone in our hospital were analyzed. Methadone was initiated from other opioids due to refractory pain in the stop-and-go switching. Among the 87 cases, 7 cases were excluded from further analysis because methadone administration was stopped due to vomiting or self-cessation within six days from switching. Results: Among the 80 cases who had methadone for seven days or more, 70 cases (SCs) were successful in switching to methadone, according to the Japanese definition, although 10 cases (UCs) who experienced the rapid progression of illness failed due to oral difficulty in the course of titration. In comparison of the clinical characteristics between SCs and UCs, the number of days alive from the start of the administration of methadone was significantly greater in the SCs than in the UCs (SCs: 87.1, UCs: 19, p  < 0.0001), but no significant differences were observed for any other factors. Conclusion: From this comparative retrospective study of opioid switching to methadone for cancer pain control between SCs and UCs, early switching to methadone may be useful for patients with advanced cancer pain.