Brazilian study compared morphine 47.4 +/- 57.6 to methadone 62.1 */- 15.5 and suggested methadone was 20% better. However, there are some problems with study.
Moreira de Barros GA, Baradelli R, Rodrigues DG, et al.
Use of methadone as an alternative to morphine for chronic pain management: a noninferiority retrospective observational study.
Pain Rep. 2021;6(4):e979.
doi:10.1097/PR9.0000000000000979
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8687725/
- 175 morphine cases; 87 methadone
- morphine 47.4 +/- 57.6; methadone 62.1 +/- 15.5
Results:
- Up Until 280 days, Morphine was superior at which time I suspect tolerance had occurred,
- In review of drug doses for neuropathic pain:
Finnerup, Nanna B., et al.
Pharmacotherapy for neuropathic pain in adults: a systematic review and meta-analysis.” The Lancet Neurology 14.2 (2015): 162-173.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4493167/We identified 13 trials of strong opioids, in which oxycodone (10–120 mg/day) and morphine (90–240 mg/day) were used mainly in peripheral neuropathic pain. The final quality of evidence was moderate. Ten trials were positive: combined NNT was 4∙3 (95% CI 3∙4–5∙8) and NNH was 11∙7 (8∙4–19∙3). Maximum effectiveness seemed to be associated with 180 mg morphine or equivalent (no additional benefit for higher doses).
My suspicion would be if the dose of morphine was adjusted to more therapeutic doses, then the difference with methadone may not have occurred after 280 days - Side Effects:
- Neuropathic pain was better managed with methadone (p = 0.02)
Comment -I have not used methadone because two different doctors in Saskatchewan were censored by our College of Physician and Surgeons for poor administration of said drug. It does appear obvious that you have to tell patient that it could take months to achieve decent control. Over 280 days, morphine doses will need to be elevated or opioid switched to a different form. Methadone might have an advantage in neuropathic pain.