Equianalgesic Dosing of Morphine to Fentanyl Transdermal Patch
According to the National Comprehensive Cancer Network (NCCN) guidelines, 60 mg/day of oral morphine is approximately equivalent to a 25 mcg/h fentanyl transdermal patch. 1
Detailed Conversion Table
The established conversion ratios between oral morphine and transdermal fentanyl patches are:
| Oral Morphine (mg/day) | Fentanyl Patch (mcg/h) |
|---|---|
| 60-134 | 25 |
| 135-224 | 50 |
| 225-314 | 75 |
| 315-404 | 100 |
This conversion table is supported by both NCCN guidelines 1 and FDA labeling 2.
Important Clinical Considerations
Patient Selection
- Fentanyl patches should only be used in opioid-tolerant patients 2
- Pain should be relatively well controlled on short-acting opioids before initiating the fentanyl patch 1
- Patches are not recommended for unstable pain requiring frequent dose changes 1, 3
Conversion Process
- Calculate the patient's total daily morphine equivalent dose
- Select the appropriate fentanyl patch strength using the conversion table
- Continue breakthrough medication during the first 12-24 hours after patch application
- Allow 2-3 days to reach steady state before making further dose adjustments 1
Safety Precautions
- Avoid heat sources (heating pads, hot baths, fever) as they accelerate fentanyl absorption and increase overdose risk 3
- Provide adequate breakthrough medication during transition (10-15% of 24-hour morphine equivalent dose) 3
- Monitor closely for respiratory depression, especially in the first 24-48 hours 3
Common Pitfalls to Avoid
Bidirectional conversion error: The conversion tables should not be used to convert from fentanyl back to other opioids, as this can lead to fatal overdose 2
Inadequate prior opioid exposure: Research shows that up to 74.1% of fentanyl patch prescriptions have been written for patients with inadequate prior opioid exposure 4
Variability in conversion calculations: Significant variation exists in opioid conversion calculations among healthcare providers, particularly for fentanyl and methadone 5
Failure to individualize: While standard conversion tables provide guidance, patient variability requires clinical judgment to titrate to the desired response 1
Special Situations
- For patients requiring doses higher than 100 mcg/h, multiple patches may be used 2
- Intermediate patch strengths (37.5 mcg/h, 62.5 mcg/h) are available for finer dose titration 2
- When converting from continuous parenteral infusion fentanyl to transdermal fentanyl, a 1:1 ratio is appropriate 1
By following these evidence-based guidelines for converting from oral morphine to transdermal fentanyl, clinicians can optimize pain control while minimizing risks of under or overdosing.