How do you convert oral morphine (opioid analgesic) to a fentanyl (synthetic opioid) patch?

Converting Oral Morphine to Fentanyl Patch

To convert oral morphine to a fentanyl patch, calculate the 24-hour oral morphine requirement and use a conversion ratio of 100:1 to determine the appropriate fentanyl patch strength. 1, 2

Step-by-Step Conversion Process

1. Calculate the total 24-hour oral morphine dose

   • Add up all oral morphine doses taken in a 24-hour period
   • If using other opioids, first convert them to oral morphine equivalents

2. Select the appropriate fentanyl patch strength using the conversion table:

Oral Morphine (mg/day)	Fentanyl Patch (mcg/hour)
60-134	25
135-224	50
225-314	75
315-404	100

1. Apply the patch and ensure it remains in place for 72 hours (3 days)

Important Clinical Considerations

• Prescribe breakthrough medication: Provide a short-acting opioid (10-15% of the 24-hour morphine equivalent dose) for breakthrough pain, especially during the first 24 hours after application 1, 3

• Monitor closely: Watch for respiratory depression in the first 24-48 hours after initial application 3

• Delayed onset: Full analgesic effect may take up to 24 hours to develop; maintain previous analgesia during this period 1

• Steady state: It may take up to 6 days (2 patch changes) to reach equilibrium on a new dose 2

• Dose adjustments: Wait at least 3 days (one full patch cycle) before increasing the initial dose 2

Special Precautions

• Patient selection: Fentanyl patches are not recommended for:

  • Opioid-naïve patients
  • Patients with unstable pain requiring frequent dose changes
  • Acute pain situations 1, 3

• Avoid heat sources: Heat (fever, heating pads, electric blankets) can accelerate fentanyl absorption and increase the risk of overdose 1, 3

• Multiple patches: For doses exceeding 100 mcg/hour, multiple patches may be used 2

• Conversion variability: Individual patient response varies; some patients may require dose adjustment after initial conversion 1, 3

Example Conversion

For a patient taking 180 mg/day of oral morphine:

1. Calculate total daily oral morphine: 180 mg/day
2. Using the conversion table, 180 mg/day falls within the 135-224 mg/day range
3. Select a 50 mcg/hour fentanyl patch
4. Prescribe breakthrough medication (e.g., immediate-release morphine 10-15 mg every 4 hours as needed)

Remember that this conversion is conservative to minimize the risk of overdose. Close monitoring and dose adjustments based on clinical response are essential for optimal pain management.