Morphine milligram equivalents (MME) is a unit of measure used to compare opioids of varying potencies.1,2 By converting different opioids to a standard value a prescriber is more able to assess a patient’s potential risk for dose-related adverse events.
The Centers for Disease Control and Prevention (CDC) found that higher doses of opioids are associated with an increased risk for motor vehicle accidents, overdose, and opioid use disorder.1 Their review of clinical trials discovered that when certain MME levels were surpassed, the risk for overdose drastically increased. Compared to opioid doses under 20 MME/day, the risk for overdose increased by a factor of 1.9 to 4.6 with doses between 50 and100 MME/day and a factor of 2.0 to 8.9 with doses over 100 MME/day. Lower doses of opioids corresponded with reduced risk for overdose; however, the CDC was unable to find evidence of a specific MME level that conferred no risk of overdose.
Further evaluation of opioid dosing regimens found that doses above 50 MME/day did not ensure improvement in patients’ function or pain, but led to greater incidences of overdose and death.1 Therefore, the CDC recommends reassessing the benefits and risks when prescribing doses above 50 MME/day. Additionally, the CDC recommends avoiding doses above 90 MME/day without clinical justification based on diagnosis and an individual needs assessment. These recommended thresholds are intended only for the treatment of chronic non-cancer pain for patients outside of palliative or end-of-life care.
Converting a patient’s total daily dose of opioids to MME is a useful tool to help identify patients who are candidates for closer monitoring or overdose risk mitigation.2 Total daily MME can be a valuable prompt to consider initiating a dose taper, educating on naloxone, or offering treatment for opioid use disorder.
1. Calculate the total daily dose of each opioid the patient is taking.
Strength per unit × Number of units/day = Total daily dose
Hydrocodone/acetaminophen 5 mg/325 mg four times daily --> 5 mg × 4 units/day = 20 mg/day hydrocodone
Oxycodone ER 15 mg twice daily --> 15 mg × 2 units/day = 30 mg/day oxycodone
2. Convert each total daily dose to MME by multiplying by its respective MME conversion factor.
Total daily dose × MME Conversion factor = Daily MME
20 mg/day hydrocodone × 1 = 20 MME/day
30 mg/day oxycodone × 1.5 = 45 MME/day
3. Add the daily MME for each opioid to get the total daily MME.
Opioid A Daily MME + Opioid B Daily MME = Today daily MME
20 MME/day + 45 MME/day = 65 MME/day
|Opioid (strength unit)||MME Conversion Factor|
|Fentanyl Transdermal (mcg/hr)||2.4|
|Methadone 1-20 (mg/day)||4|
|Methadone 21-40 (mg/day)||8|
|Methadone 41-60 (mg/day)||10|
|Methadone ≥ 61-80 (mg/day)||12|
Conversion factors are approximate values and variations do exist among available MME conversion tables.2
Fentanyl is converted to MME differently than other opioids. The daily MME for fentanyl is calculated by multiplying the strength of the transdermal patch in mcg/hour by the MME conversion factor for fentanyl. For example, if a patient is on fentanyl 50 mcg/hour transdermal patch, the daily MME would be 50 mcg/hour × 2.4 = 120 MME/day.2
The MME conversion factor for methadone increases with higher daily doses.2
Opioid doses that have been converted to MME should not be used directly for converting one opioid to another as these conversions provide equivalency information only and do not account for incomplete cross-tolerance between opioids and individual patient differences that impact pharmacokinetics of opioids.2
Jonathan Samardzich, PharmD
University of Illinois at Chicago College of Pharmacy
The information presented is current as of November 2019. This information is intended as an educational piece and should not be used as the sole source for clinical decision-making.
Posted on Jan. 27, 2020