Use of Methadone for Cancer Pain Management in a Tertiary Cancer Care Centre: A Retrospective Observational Cohort Study

Background and Aims: Cancer pain significantly impacts patient well-being, with a high prevalence in India. While the World Health Organisation pain ladder is effective, a substantial proportion of patients experience opioid-refractory pain. Methadone, with its unique multi-modal analgesic mechanisms such as mu-receptor agonism, N-Methyl-D-Aspartate antagonism and serotonin/norepinephrine reuptake inhibition, offers a valuable option for such cases, despite its variable pharmacokinetics and potential for adverse effects, such as corrected QT (QTc) prolongation. Methods: This retrospective audit was conducted on a prospectively maintained database of 29 adult cancer patients with chronic pain who received methadone at a tertiary cancer care centre in India from March 2023 to June 2024. Demographics, pain severity (numeric rating scale, [NRS]), prior opioid use, methadone dosing regimens and reported adverse effects were collected. Institutional Review Board approval was obtained, with a waiver of individual consent. Results: At methadone initiation, 27 out of 29 patients reported severe pain (NRS 7-10). The majority had a neuropathic pain component. Twenty-seven patients were on strong opioids, of whom 22 were switched to methadone due to inadequate pain control. Methadone was most commonly started at 15–20 mg/day, at 6 to 8 hourly intervals. Two out of 28 patients who came for the first follow-up after initiation of methadone reported severe pain, resulting in a meaningful reduction in severe pain prevalence. By the second follow-up, attrition of 8 of 29 patients was noted, attributable to disease progression, inability to report to the pain clinic due to functional decline and death. One patient developed QTc prolongation (>463 ms) at 45 mg/day. Constipation was the most commonly reported adverse effect, resulting in a few discontinuations. Conclusion: Methadone is effective for refractory cancer pain. Its use requires cautious initiation and titration due to inter-individual variability and adverse effects like QTc prolongation. This audit highlights methadone’s utility in a real-world clinical setting.