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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:
| 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:
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Ayonrinde OT, Bridge DT. The rediscovery of methadone for cancer pain management. Med J Aust 2000;173:538.
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D'Amato SL. Methadone Rediscovered. Maine Link. Maine Center for Cancer Medicine and Blood Disorders.
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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.
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Goodman F, Jones W, Glassman P. Methadone dosing recommendations for treatment of chronic pain. Veterans Health Administration.
VA Dosing Recommendations
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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.
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Mancini I, Lossignol DA, Body JJ. Opioid switch to oral methadone in cancer pain. Current Opinion in Oncology. 2000;12:308-313.
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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.
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Mercadante S. Morphine versus methadone in the pain treatment of advanced-cancer patients followed up at home. J Clin Oncol 1998:16(11):3656.
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Washington State Pharmacy & Therapeutics Committee. Opioid Dosing Guideline 2003. Available at:
WA P&T Opioid Dosing Guideline (PDF)
← Return to the Opioid Calculator page.
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