Hydromorphone to Morphine Milligram Equivalent (MME) Conversion
1 mg of hydromorphone equals 4 mg of morphine in MME terms. 1
Conversion Factors for Opioid Equivalence
- According to the CDC Guideline for Prescribing Opioids for Chronic Pain, hydromorphone has a conversion factor of 4 when calculating morphine milligram equivalents (MME) 1
- This means that to calculate the MME for hydromorphone, you multiply the hydromorphone dose by 4 1
- For example, 1 mg of hydromorphone = 4 mg MME 1
Clinical Application of Conversion Factors
- When converting between opioids, these conversion factors help clinicians maintain appropriate analgesic effect while minimizing adverse effects 2
- The potency of hydromorphone (approximately 5-7 times more potent than morphine) allows for smaller volume administration, which may be beneficial in certain clinical scenarios 2
- For IV to oral conversions, hydromorphone has different conversion ratios than the MME calculation used for comparing potency 3
Route-Specific Considerations
- When converting from IV morphine to IV hydromorphone, a ratio of approximately 5:1 is recommended (10 mg IV morphine = 2 mg IV hydromorphone) 2
- For oral to parenteral hydromorphone conversions, a ratio of approximately 5:1 is supported (oral hydromorphone has approximately one-fifth the potency of parenteral hydromorphone) 4
- The FDA clinical studies indicate that 5 mg and 10 mg of oral hydromorphone provided pain relief comparable to 30 mg and 60 mg of oral morphine sulfate, respectively 5
Research Findings on Conversion Ratios
- Some research suggests that the morphine to hydromorphone ratio may be closer to 3:1 in clinical practice with prolonged patient-controlled analgesia, differing from the standard 4:1 or 5:1 ratios 6
- A Japanese study investigated morphine to hydromorphone conversion ratios of 1:5 and 1:8, finding that both ratios maintained adequate pain control when switching between medications 7
- For higher doses of IV hydromorphone (≥30 mg/day), a lower conversion ratio to other opioids may be required 3
Common Pitfalls and Caveats
- Conversion ratios are approximate guides, and clinical judgment is essential when converting between opioids 4
- These conversion factors are specifically for calculating MME for comparison purposes and may differ from equianalgesic dosing when switching patients between medications 1, 2
- When converting between opioids, incomplete cross-tolerance should be considered, which may require dose reduction when switching to a new opioid 2
- Patients should be monitored closely after conversion for both pain control and potential adverse effects 4