Does a fentanyl (transdermal opioid analgesic) patch have an oral morphine (opioid analgesic) equivalent?

From the Guidelines

A fentanyl transdermal patch does have an oral morphine equivalent, with a conversion factor of 2.4, as indicated in the CDC clinical practice guideline for prescribing opioids for pain - United States, 2022 1. When converting between these medications, healthcare providers use equianalgesic conversion tables to determine appropriate dosing.

• The conversion factor for fentanyl transdermal is 2.4, meaning that for every 1 mcg/hr of fentanyl, it is equivalent to 2.4 mg of oral morphine.
• For example, a fentanyl patch delivering 25 mcg/hour is approximately equivalent to 60 mg of oral morphine per day.
• The conversion is not perfectly linear across all doses, and individual patient factors must be considered.
• When switching from oral morphine to a fentanyl patch, the total 24-hour morphine dose is calculated first, then converted to the appropriate fentanyl patch strength. It's essential to note that fentanyl is significantly more potent than morphine, which is why the patch delivers micrograms rather than milligrams.
• Due to this potency difference and fentanyl's unique pharmacokinetics, conversions should be done cautiously, typically with dose reductions of 25-50% when switching between opioids to account for incomplete cross-tolerance.
• Patients should be monitored closely after conversion, as individual responses to opioids can vary significantly based on factors like age, organ function, and prior opioid exposure, as supported by the management of cancer pain in adult patients: ESMO clinical practice guidelines 1 and adult cancer pain guidelines 1.

From the FDA Drug Label

In addition, patients who are not opioid-tolerant have experienced hypoventilation and death during use of fentanyl transdermal system. Therefore, fentanyl transdermal system should be used only in patients who are opioid-tolerant To convert patients from oral or parenteral opioids to fentanyl transdermal system, use Table C: Alternatively, for adult and pediatric patients taking opioids or doses not listed in Table C, use the following methodology: Calculate the previous 24-hour analgesic requirement. Convert this amount to the equianalgesic oral morphine dose using Table D Table E displays the range of 24-hour oral morphine doses that are recommended for conversion to each fentanyl transdermal system dose.

TABLE E* RECOMMENDED INITIAL FENTANYL TRANSDERMAL SYSTEM DOSE BASED UPON DAILY ORAL MORPHINE DOSE

Oral 24-hour Morphine (mg/day)Fentanyl Transdermal System Dose (mcg/hr) 60-13425 135-224 50 225-314 75 315-404 100 405-494 125 495-584 150 585-674 175 675-764 200 765-854 225 855-944 250 945-1034 275 1035-1124 300

The fentanyl patch has an oral morphine equivalent. The conversion can be done using Table E, which displays the range of 24-hour oral morphine doses that are recommended for conversion to each fentanyl transdermal system dose.

• For example, a daily oral morphine dose of 60-134 mg is equivalent to a 25 mcg/hr fentanyl transdermal system dose.
• A daily oral morphine dose of 135-224 mg is equivalent to a 50 mcg/hr fentanyl transdermal system dose.
• A daily oral morphine dose of 225-314 mg is equivalent to a 75 mcg/hr fentanyl transdermal system dose.
• A daily oral morphine dose of 315-404 mg is equivalent to a 100 mcg/hr fentanyl transdermal system dose. The conversion ratio is based on clinical experience and studies in patients with chronic pain 2.

From the Research

Fentanyl Patch and Oral Morphine Equivalent

• The fentanyl patch is a transdermal opioid analgesic that can be prescribed to replace morphine preparations 3.
• The conversion ratio from morphine to fentanyl has been claimed to be 100:1 or 150:1, but individual variations may exist 3.
• A study found that the mean conversion ratio was 96.6, with a wide variation among patients 3.
• Another study suggested that the efficacy ratio of fentanyl patch to oral morphine is 80:1, indicating that oral morphine of 25-75 mg/d should be substituted with a fentanyl patch preparation at a dose of 2.5 mg/3 d 4.
• A retrospective cohort study compared equipotent doses of transdermal fentanyl and transdermal buprenorphine in patients with cancer and noncancer pain, and found that the equipotency ratio of transdermal fentanyl to oral morphine is 1:100 5.

Conversion Ratio Variations

• The conversion ratio from morphine to fentanyl can vary among patients, and individual factors should be considered when switching from oral morphine to a fentanyl patch 3, 4.
• A study found that women and patients 65 years of age and older were more likely to have inadequate prior opioid exposure when prescribed a fentanyl patch, highlighting the need for careful consideration of individual factors when converting from oral morphine to a fentanyl patch 6.
• The safety of fentanyl initiation improved over a study period, but still, half of fentanyl patch prescriptions were written for patients with inadequate prior opioid exposure, emphasizing the importance of careful conversion and monitoring 6.

Clinical Implications

• The fentanyl patch is a useful agent for controlling severe cancer pain, with excellent analgesic effects, fewer adverse effects, and more convenience, especially when transitioning patients to home care or avoiding oral administration 3.
• However, the use of transdermal fentanyl as a first-choice strong opioid, even when oral administration is possible, has been observed in some settings, highlighting the need for careful consideration of individual patient needs and guidelines 7.