Morphine Milligram Equivalent (MME) of IV Hydromorphone
The MME conversion factor for IV hydromorphone is 4, meaning 1 mg of IV hydromorphone equals 4 mg of oral morphine equivalents. 1
Standard Conversion Factor
- The CDC Guideline for Prescribing Opioids for Chronic Pain establishes that hydromorphone has a conversion factor of 4 when calculating morphine milligram equivalents (MME). 1
- This means that 1 mg of hydromorphone = 4 mg MME, regardless of route of administration for MME calculation purposes. 1
Clinical Context and Potency Considerations
While the MME conversion factor is standardized at 4:1 for calculation purposes, it's important to understand that actual clinical potency varies by route:
- For equianalgesic dosing conversions (not MME calculations), IV morphine to IV hydromorphone uses approximately a 5:1 ratio, where 10 mg IV morphine equals 2 mg IV hydromorphone. 2, 3
- Research data suggests IV hydromorphone may be 8.5 times as potent as IV morphine on a milligram basis in actual clinical practice. 4
- The higher clinical potency (5-7 times more potent than morphine) allows for smaller volume administration, which is beneficial in acute care settings. 2
Important Distinction
- The MME conversion factor of 4 is specifically for calculating total morphine milligram equivalents for comparison and monitoring purposes, such as tracking opioid burden or regulatory compliance. 1
- This differs from equianalgesic dosing ratios used when actually switching patients between medications, where incomplete cross-tolerance must be considered and doses should be reduced by 25-50%. 3, 1
- When converting between opioids in clinical practice, the 5:1 ratio (IV morphine to IV hydromorphone) with dose reduction for incomplete cross-tolerance is recommended, not the MME factor. 2, 3