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Methadone Conversion Factors


There is a difference in conversion factors for methadone when used for acute vs. chronic pain. Methadone exhibits a non-linear relationship due to the long half-life and accumulates with chronic dosing. You may see a dramatic increase in MED depending on the dose. The conversion factors for methadone in the AMDG calculator are based on chronic dosing and as follows:


Methadone (Methadose, Dolophine) Factor
up to 20mg per day 4
21 to 40mg per day 8
41 to 60mg per day 10
> 60mg per day 12

The following are references for methadone conversion:


  • Ayonrinde OT, Bridge DT. The rediscovery of methadone for cancer pain management. Med J Aust 2000;173:538.
  • D'Amato SL. Methadone Rediscovered. Maine Link. Maine Center for Cancer Medicine and Blood Disorders.
  • Davis MP, Walsh D. Methadone for relief of cancer pain: a review of pharmacokinetics, pharmacodynamics, drug interactions and protocols of administration. Support Care Cancer 2001; 9:73-83.
  • Goodman F, Jones W, Glassman P. Methadone dosing recommendations for treatment of chronic pain. Veterans Health Administration. VA Dosing Recommendations
  • Laur DF. A comparison of intraoperative morphine sulfate and methadone on postoperative visual analogue scale pain scores and narcotic requirements. CRNA 1995;6(1):21.
  • Mancini I, Lossignol DA, Body JJ. Opioid switch to oral methadone in cancer pain. Current Opinion in Oncology. 2000;12:308-313.
  • Mellar PD, Declan W. Methadone for relief of cancer pain: a review of pharmacokinetics, pharmacodynamics, drug interactions and protocols of administration. Support care cancer. 2001:9:73-83.
  • Mercadante S. Morphine versus methadone in the pain treatment of advanced-cancer patients followed up at home. J Clin Oncol 1998:16(11):3656.
  • Washington State Pharmacy & Therapeutics Committee. Opioid Dosing Guideline 2003. Available at: WA P&T Opioid Dosing Guideline (PDF)

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