Methadone Conversion Using a 3-Day Switch Strategy in Patients with Cancer on High-Dose Opioids: A Retrospective Study.

Introduction: Methadone has shown effectiveness in pain control in patients with cancer who are intolerant to other opioids in China. However, the optimal strategy for methadone conversion from previous high doses of opioids in refractory cancer pain remains debatable. This study aimed to describe the efficacy and safety of a 3-day switch (3DS) strategy for methadone conversion in patients with refractory cancer pain on high doses of opioids.

Methods: We retrospectively reviewed 30-day medical records of 70 patients with refractory cancer pain who used a 3DS strategy for methadone conversion from previous high doses of opioids from July 2018 to December 2022. The 3DS strategy indicated that the methadone dose was increased by one third every day for 3 days. Data on the rate of successful conversion, the time to stable analgesia after conversion, the conversion efficiency, the corrected QT (QTc) interval, the actual conversion ratios, adverse events (AEs), and quality of life were analyzed.

Results: Seventy patients received 3DS methadone conversion and 64 patients were eligible for analysis. Fifty patients (78%) achieved stable analgesia, and the median time to stable analgesia was 8.14 ± 2.70 (range 6-14) days. The average dose of methadone was 77.94 ± 42.74 mg. The most common AEs (≥ 10%) included constipation, dry mouth, nausea, and cold sweats. The incidence of constipation was reduced post-methadone conversion, and a statistically significant but asymptomatic prolongation of the QTc interval was observed. Additionally, the actual conversion ratios were lower than Ayonrinde's recommended ratios.

Conclusions: The 3DS strategy for methadone conversion is applicable in Chinese patients with refractory cancer pain on high doses of opioids.