Approximate guide only, based on NICE opioid conversion ratios to oral morphine. Individual response
to opioids varies. When switching opioids, consider reducing the calculated equivalent dose to account
for incomplete cross-tolerance, and monitor closely. Seek specialist palliative care or pain team advice
for complex cases, high doses, or if uncertain. Do not use this table to derive conversion ratios directly
between two other drugs, always convert via oral morphine as shown here.
Dose (mg):
Buprenorphine transdermal patch
Patches only come in fixed strengths (5, 10, 15, 20, 35, 52.5, 70 micrograms/hour). Formulations are
available as 7-day, 3-day (72-hourly), and 4-day (96-hourly) patches. Prescribe by brand, dose, and duration.
Fentanyl transdermal patch
Patches only come in fixed strengths (12, 25, 37.5, 50, 75, 100 micrograms/hour), as 72-hourly patches.
Prescribe by brand, dose, and duration. Based on the Palliative Care Formulary 9th edition.
Starting a fentanyl patch
Do not start in the last days of life.
Choose a suitable patch, a matrix patch allows titration in smaller increments.
Calculate the dose of fentanyl from the conversion chart above or seek advice. Patch strengths can be combined to provide an appropriate dose.
Patches are licensed for dose initiation and titration.
Make sure the patient takes another regular opioid for the first 12 hours after the patch is first applied to allow the fentanyl to reach therapeutic levels (see the switching table below).
An immediate release opioid (for example oral morphine or morphine SC) must be available 1 to 2 hourly, as required, for breakthrough pain or to treat any opioid withdrawal symptoms (diarrhoea, abdominal pain, nausea, sweating). These can occur during the fentanyl initiation period due to the variable time to reach steady state. The correct 4 hourly equivalent dose should be used.
Fentanyl is often less constipating than morphine, half dose of any laxative and titrate.
Switching opioid to fentanyl patch
Current opioid
Switching procedure
Immediate release (quick acting) morphine or oxycodone
Apply patch, continue the immediate release opioid 4 hourly for the next 12 hours.
Modified release (long acting) 12 hourly morphine or oxycodone
Apply patch when the last dose of a 12 hourly, modified release opioid is given.
Subcutaneous infusion of morphine, diamorphine, oxycodone or alfentanil
Apply the patch and continue the infusion for the next 8 to 12 hours, then stop the infusion.
Adjusting the fentanyl patch dose
Review the fentanyl patch dose after 72 hours, drug levels will be at steady state.
If the patient shows signs of opioid toxicity (drowsiness, confusion), reduce the dose and reassess the pain. Seek advice.
If the patient still has pain which is opioid responsive, titrate the fentanyl dose in 12 microgram to 25 microgram/hour increments depending on the patch strength in use. Remember to include the breakthrough doses used. It will take 12 to 24 hours for the new dose to take effect so give breakthrough analgesia at the correct dose, as required. If there is a significant increase in the number of breakthrough doses required, seek specialist advice.
Fentanyl patches in the last days of life
Continue the fentanyl patch, changing it every 72 hours.
If a new, opioid responsive pain develops, use subcutaneous morphine as required for breakthrough pain. Use the conversion chart above to calculate the dose of morphine. If the patient is known to be renally impaired, alfentanil may be a more appropriate choice (eGFR less than 20ml/min, although specialists may recommend earlier).
After 24 hours, the breakthrough doses of morphine given in that period can be totalled and this dose of morphine administered as an SC infusion in a syringe pump over the next 24 hours in addition to the fentanyl patch.
Switching a fentanyl patch
If switching from a fentanyl patch to any other strong opioid by any other route, specialist palliative care advice should be sought.
Status: Not set
Last reviewed: Not set
Next review due: Not set
Why use
Standardises opioid dose conversion using oral morphine equivalent as the common reference point.
When to use
Use when switching a patient between opioids or routes, or when converting to a buprenorphine or fentanyl patch.
How to use
For oral or parenteral conversion, select the drug and route being converted from and enter the dose.
Result shows the oral morphine equivalent and a table of the equivalent dose for every other drug and route.
For a buprenorphine or fentanyl patch, enter the total daily oral morphine dose in the relevant section.
If there is no exact match, the nearest available patch strengths above and below are shown instead of an invented value.
Click Copy to copy the oral or parenteral conversion result.
Pitfalls and drawbacks
Approximate guide only. Does not account for incomplete cross-tolerance when switching opioids, a dose reduction is often appropriate and is a clinical decision, not something this tool applies automatically. Transdermal patches only come in fixed strengths, doses that fall between listed strengths have no exact equivalent and are shown as a range rather than an invented value.
Advice
Always convert via oral morphine equivalent rather than deriving a ratio directly between two other drugs. Seek specialist palliative care or pain team advice for complex cases, high doses, or doses above the thresholds flagged for buprenorphine and fentanyl patches.
Evidence
Conversion ratios and patch dose equivalences based on NICE opioid conversion guidance and the Palliative Care Formulary 9th edition.