Overview
Why Equivalency Is Only a Starting Estimate
Equianalgesic conversion expresses the analgesic exposure from different opioids or routes against a common morphine standard.
Equianalgesic conversion expresses the analgesic exposure from different opioids or routes against a common morphine standard. The comparison is useful because opioids differ in mu-receptor potency, oral bioavailability, metabolism, and active metabolites. It is not a guarantee that two calculated doses will produce the same analgesia or the same respiratory effect in one patient. A conversion table is a population average. Age, organ function, previous opioid exposure, genetics, pain type, drug interactions, and incomplete cross-tolerance can all change the patient’s response. Use the result to frame a cautious starting plan, not to generate an automatic prescription. Morphine milligram equivalents per day, or MME/day, are primarily a way to compare opioid exposure and identify increasing overdose risk. MME is not a direct opioid-rotation calculator. The CDC specifically warns that using MME factors to switch a patient directly to the calculated dose of another opioid can overestimate the new dose and cause overdose. The 2022 US guidance does not impose an absolute 90 MME/day limit. It does recommend heightened caution before increasing a dosage to 50 MME/day or more, with an individualized...