Conversion of IV Hydromorphone to Oral Morphine
36 mg of IV hydromorphone in 24 hours is equivalent to approximately 432 mg of oral morphine per day. When converting from IV hydromorphone to oral morphine, use a conversion ratio of approximately 1:12, meaning 1 mg of IV hydromorphone equals approximately 12 mg of oral morphine.
Conversion Calculation Process
Step 1: Calculate the IV hydromorphone to oral morphine conversion
- The conversion ratio from IV hydromorphone to oral morphine equivalent daily dose (MEDD) is approximately 1:11.46 1
- 36 mg IV hydromorphone × 11.46 = 412.56 mg oral morphine
Step 2: Account for dose-dependent considerations
- For higher doses of IV hydromorphone (≥30 mg/day), a slightly lower conversion ratio of 1:9.86 may be more appropriate 1
- Using this adjusted ratio: 36 mg × 9.86 = 354.96 mg oral morphine
Step 3: Round to a practical dose
- Based on the calculations above, a reasonable oral morphine equivalent would be approximately 360-410 mg/day 1
Important Clinical Considerations
Cross-tolerance: When converting between different opioids, incomplete cross-tolerance may require dose reduction of 25-50% from the calculated equianalgesic dose 2
Monitoring: Close monitoring for both pain control and adverse effects is essential after opioid conversion 2
Dosing schedule: Consider dividing the total daily oral morphine dose into multiple doses (e.g., every 4 hours for immediate release or every 12 hours for extended release) 2
Side effect management: Prophylactic laxative therapy should be initiated to prevent opioid-induced constipation 3
Common Pitfalls to Avoid
Conversion variability: Conversion ratios are approximate guides, and clinical judgment is essential when converting between opioids 2
Individual factors: Patient-specific factors such as age, renal function, and prior opioid exposure can affect the appropriate conversion ratio 2
Dose adjustments: The calculated dose may need adjustment based on the patient's clinical response 1
Route-specific considerations: The bioavailability of oral morphine is approximately 30%, which is accounted for in the conversion ratio 4