Use of methadone as an alternative to morphine for chronic pain management: a noninferiority retrospective observational study

INTRODUCTION: Chronic pain causes disability and is prevalent in the general population. Opioids are a part of a multimodal strategy for pain management. Methadone, a cheap and long-acting synthetic opioid, may represent an option for those who have limited access to the aforementioned class of analgesics. We aimed to provide a real-world evidence for the analgesic use of methadone, compared with morphine. METHODS: We conducted a noninferiority, retrospective observational single center study of patients with chronic pain, managed with either methadone or morphine at an outpatient specialized clinic. We extracted data from the electronic health records of patients who underwent an active treatment between August 2012 and January 2020 and were examined for at least 2 consecutive medical visits, after the administration of one of the aforementioned drugs. Data were analyzed using a generalized additive model with random-effects mixed linear method to account for the individual-related, time-related, and drug-related variations. The numeric verbal scale (0–10) was used to assess the pain severity. RESULTS: From the database of 3373 patients, we included 262 patients (175 methadone and 87 morphine). In an unadjusted analysis, methadone was superior to morphine, and the mean worst pain was 0.86 points lower (95% confidence interval, −1.29 to −0.43). Moreover, methadone was superior to morphine in the adjusted analysis, with the worst pain mean being 1.24 points lower. This provided evidence for the noninferiority of methadone than morphine. CONCLUSION: Methadone was superior to morphine in a 20% noninferiority margin for reducing worst pain.