Why doesn’t the FDA use MME in professional literature on dosing an opioid

The FDA does not routinely use Morphine Milligram Equivalents (MME) in its professional literature for opioid
dosing for several key reasons:
– **Variability in Conversion Factors:** MME conversion tables are based on data from small clinical studies
in limited populations, and different resources (tables, calculators) may use different conversion factors for the
same opioid. This lack of standardization can lead to inconsistencies and potential dosing errors when applied
broadly[5].
– **Patient and Drug Differences:** The pharmacokinetics and pharmacodynamics of opioids can vary widely
among individuals due to factors like opioid tolerance, genetics, age, organ function, and concurrent
medications. Some opioids (e.g., partial agonists like buprenorphine or novel agents like tapentadol) do not fit
neatly into the MME system, making it unreliable for all clinical scenarios[5].
– **Intended Use of MME:** The original purpose of MME was to provide a rough guide for clinicians when
converting from one opioid to another, not as a precise tool for dosing or setting rigid prescribing thresholds[5].
Over time, MMEs have been increasingly used by policymakers and payers to set limits, but these uses may not
reflect the nuances required for individual patient care.
– **Risk of Misapplication:** The FDA and CDC have both cautioned that applying MME thresholds as rigid
standards can lead to unintended consequences, such as under-treatment of pain or abrupt discontinuation of
opioids in patients who may benefit from them. Clinical guidelines now emphasize individualized care and warn
against using MME cutoffs as inflexible rules[1][5].
– **Epidemiologic vs. Clinical Use:** While epidemiologic studies have shown that higher daily MME doses
are associated with increased overdose risk, there is no universally agreed-upon MME threshold that defines
“safe” versus “unsafe” prescribing. The FDA recognizes that MME is useful for population-level risk
assessment but not as a precise clinical dosing tool[5].

In summary, the FDA avoids emphasizing MME in professional dosing literature because of its limitations in accuracy, variability among individuals and drugs, and the risk of misapplication in clinical practice. Instead, the FDA and other agencies encourage individualized, evidence-based opioid prescribing that considers the unique needs and risks of each patient[1][5].

Citations:
[1] https://www.cdc.gov/mmwr/volumes/71/rr/rr7103a1.htm
[2] https://www.ncbi.nlm.nih.gov/books/NBK458653/
[3] https://www.fda.gov/media/147152/download
[4] https://www.cdc.gov/mmwr/volumes/65/rr/rr6501e1.htm
[5] https://www.fda.gov/media/150436/download
[6]
https://www.fda.gov/drugs/news-events-human-drugs/morphine-milligram-equivalents-current-applications-and
-knowledge-gaps-research-opportunities-and
[7]
https://www.fda.gov/drugs/drug-safety-and-availability/fda-updates-prescribing-information-all-opioid-pain-me
dicines-provide-additional-guidance-safe-use
[8] https://www.fda.gov/media/126835/download
[9]
https://www.fda.gov/drugs/fda-drug-safety-podcasts/fda-updates-prescribing-information-all-opioid-pain-medici
nes-provide-additional-guidance-safe-use
[10] https://www.healthvermont.gov/sites/default/files/document/reg-prescribing-opioids.pdf
[11] https://www.ncbi.nlm.nih.gov/books/NBK551720/
[12] https://www.ncbi.nlm.nih.gov/books/NBK572085/
[13] https://health.ri.gov/addiction-overdose/safe-opioid-prescribing
[14] https://www.accessdata.fda.gov/drugsatfda_docs/label/2008/019813s033lbl.pdf
[15] https://www.ncbi.nlm.nih.gov/books/NBK458654/
[16] https://mn.gov/dhs/opip/opioid-guidelines/pain-phase/acute-pain.jsp
[17] https://healthandwelfare.idaho.gov/providers/opioid-use-disorder/opioid-prescribing
[18] https://mn.gov/dhs/opip/opioid-guidelines/pain-phase/chronic-pain.jsp
[19]
https://www.fda.gov/drugs/food-and-drug-administration-overdose-prevention-framework/timeline-selected-fda
-activities-and-significant-events-addressing-substance-use-and-overdose
[20] https://www.hca.wa.gov/assets/billers-and-providers/opioid-policy.pdf
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