Converting Oral Hydromorphone to Subcutaneous Dosing

Conversion Calculation

• The total daily subcutaneous dose should be calculated by dividing the total daily oral hydromorphone dose by 5, resulting in a dose of 0.4 mg/day, which is then divided by 6 to get a subcutaneous dose of 0.067 mg, rounded to 0.1 mg every 4 hours, according to the National Comprehensive Cancer Network guidelines 1

Evidence Supporting Conversion Ratios

• The National Comprehensive Cancer Network guidelines support a conversion ratio of approximately 5:1 when converting from oral to parenteral hydromorphone, noting that oral hydromorphone has approximately one-fifth the potency of parenteral hydromorphone 1, 2
• Parenteral administration bypasses first-pass metabolism, requiring accounting for bioavailability differences when converting between routes of administration 3

Special Considerations

• Patients should be monitored closely after conversion for both pain control and potential adverse effects, with rescue medication potentially needed during the transition period until stable analgesia is achieved, as recommended by the National Comprehensive Cancer Network 1, 2

Potential Pitfalls and Caveats

• Conversion ratios are approximate guides, and clinical judgment is essential when converting from oral to subcutaneous hydromorphone, according to the National Comprehensive Cancer Network guidelines 1
• The subcutaneous route provides more consistent absorption compared to oral administration, which may affect the timing and intensity of pain relief 3

Monitoring After Conversion

• If pain control is inadequate, the dose may be increased by 25-50%, and patients should be monitored for common opioid-related adverse effects such as respiratory depression, constipation, and nausea, as recommended by the National Comprehensive Cancer Network 1, 4