MME Conversion Factor for Oral Morphine
The conversion factor for oral morphine is 1.0, meaning that oral morphine serves as the reference standard for calculating morphine milligram equivalents (MME). 1
Understanding the Conversion
- Oral morphine has a conversion factor of 1.0, which means that 1 mg of oral morphine equals 1 MME. 1
- This makes morphine the reference opioid against which all other opioids are compared when calculating MME. 2
- To calculate MME for oral morphine, simply multiply the total daily dose in milligrams by 1.0. 1
Practical Application
For example, if a patient takes 90 mg of oral morphine daily, this equals 90 MME per day. 2
- The calculation is straightforward: 90 mg × 1.0 = 90 MME. 2
- This applies to both immediate-release and modified-release formulations of oral morphine. 1
Clinical Context for MME Calculations
- MME calculations are used primarily for risk assessment and monitoring, not for direct opioid conversion between medications. 1, 2
- The CDC recommends using caution when prescribing opioids at any dosage and carefully reassessing before increasing total opioid dosage to ≥50 MME/day. 1
- When total MME exceeds 90 MME/day, careful monitoring for respiratory depression and other adverse effects is recommended. 2
Important Caveats
- Equianalgesic dose conversions are only estimates and cannot account for individual variability in genetics and pharmacokinetics. 1
- When converting from one opioid to another, the new opioid should be dosed substantially lower than the calculated MME dose to avoid overdose due to incomplete cross-tolerance. 1
- MME calculations should not be used to determine actual doses when rotating between opioids—this requires dose reduction of 25-50% or more. 2