Fentanyl (transdermal patch) to Morphine: how to convert safely
Bottom line
Each 25 mcg/h of transdermal fentanyl ≈ 60–90 mg oral morphine equivalents/day. Fentanyl conversions use ranges, not a single factor — and patches are only for opioid-tolerant patients (≥60 OME/day for ≥1 week).
Patch sizes vs. morphine equivalents
| Patch (mcg/h) | ≈ OME (mg/day) | ≈ oral morphine (mg/day) |
|---|---|---|
| 12 | 29–43 | 29–43 |
| 25 | 60–90 | 60–90 |
| 37 | 89–133 | 89–133 |
| 50 | 120–180 | 120–180 |
| 62 | 149–223 | 149–223 |
| 75 | 180–270 | 180–270 |
| 100 | 240–360 | 240–360 |
Ranges reflect the commonly used 25 mcg/h ≈ 60–90 OME/day equivalence; verify against your institutional table.
Method: rotating off the patch
- Convert the current patch to an OME range using the table above.
- Remove the patch; remember a skin depot keeps releasing drug for 12–24 h.
- Start the new opioid at a reduced dose (25–50% below the calculated equivalent) no sooner than 12–18 h after removal.
- Use short-acting PRN doses to bridge, and monitor for stacking sedation in the first 24 h.
Cautions
- Fentanyl patches are only for opioid-tolerant patients (≥60 OME/day for ≥1 week). Applying a patch to an opioid-naïve patient can be fatal.
- Absorption takes 12–24 h to reach steady state and continues 12–24 h after removal — overlap short-acting coverage on the way up, and do not stack doses on the way down.
- Fever, external heat sources, and broken skin all increase absorption unpredictably.
- Active metabolites (M3G/M6G) accumulate in renal impairment — avoid or dose-reduce morphine when eGFR is reduced, and consider an alternative agent in dialysis patients.
- Histamine release can cause pruritus and hypotension, which is not a true allergy but is often documented as one.
Build the full regimen
The opioid regimen builder handles fentanyl patch selection from a mixed home regimen, including rounding to available patch sizes and frail-patient reductions.
Frequently asked questions
- How many mg of morphine equals a 25 mcg/h fentanyl patch?
- A 25 mcg/h fentanyl patch corresponds to roughly 60–90 mg oral morphine equivalents per day, which is about 60–90 mg/day of oral morphine. Fentanyl conversions use ranges, not a single factor, because absorption varies between patients.
- Who should NOT be started on a fentanyl patch?
- Opioid-naïve patients. Transdermal fentanyl is only appropriate for patients already tolerant to at least ~60 mg oral morphine equivalents per day for a week or more. Starting a patch in a naïve patient can cause fatal respiratory depression.
- How long after removing a fentanyl patch does fentanyl keep absorbing?
- A subcutaneous depot keeps releasing fentanyl for 12–24 hours after patch removal. When rotating off a patch, start the new opioid at a reduced dose no sooner than 12–18 hours after removal, and monitor for stacking sedation.
Créé et maintenu par Yasmine Abbey, MD, MSc · Dernière revue:
Aide éducative à la décision destinée aux cliniciens. Ne constitue pas un avis médical — vérifiez les résultats au regard de votre jugement clinique, des protocoles de votre établissement et des recommandations en vigueur.