Opioid Dose Calculator

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. http://www.pbm.va.gov/clinicalguidance/clinicalrecommendations/MethadoneDosingRecommendations.pdf
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)

CAUTION: This calculator should NOT be used to determine doses when converting a patient from one opioid to another. This is especially important for fentanyl and methadone conversions. Equianalgesic dose ratios are only approximations and do not account for genetic factors, incomplete cross-tolerance, and pharmacokinetics.

This opioid dose calculator was developed by the Washington State Agency Medical Directors' Group to be used in conjunction with the Interagency Guideline on Prescribing Opioids for Pain. For more info, please refer to the guideline at: AMDG - 2015 Guidelinehttps://amdg.wa.gov/guidelines

For technical questions or comments, please contact: AMDG Web SupportAMDG IT Support at wisj235@lni.wa.gov. Please note: this calculator is not compatible with IE 7 or below.