Opioid Dose Calculator

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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:

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.

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