Oh Fentanyl Patch

Hey there 👋🏻

If you work in the inpatient setting and want to avoid some common mistakes you might already be making, check out our VuMedi video on the 5 inpatient pain management oversights. It’s only 12 minutes—perfect for your commute or lunch break.

A few weeks ago, I had a case involving fentanyl patches. A patient with end-stage cancer had just started on an opioid, and within 24 hours of admission I saw this:

Fentanyl patch 50 mcg/hr.

Whenever I see a fentanyl patch, so many questions come to mind as a pain management pharmacist:

• Why does the patient need it?

• What have they been taking?

• Is it newly started or a continuation?

• Do they have support at home to use it safely?

Dosing a fentanyl patch isn’t as simple as picking a random dose or doubling it. Thankfully, Fast Facts (one of my favorite palliative and pain resources) offers helpful guidance on fent patch dosing.

The Manufacturer Label Conversion

If you’ve never looked at the fentanyl patch drug label, it includes a conversion guide.

Duragesic Prescribing Information. US Food & Drug Administration. http://www.accessdata.fda.gov/drugsatfda_docs/label/2005/19813s039lbl.pdf. Accessed August 18,2025

Now, here are a couple of disclaimers from the label:

1. The conversion is conservative.

2. Using the table to convert from fentanyl patch to another opioid will overestimate.

Fast Fact’s take: The FDA label is conservative, so it’s better for older, frailer patients or those at higher risk of overdose (sleep apnea, interacting meds).

The Breitbart Formula Conversion

A quick and simple way to convert to a fentanyl patch is to assume that 2 mg of total daily oral morphine equivalents (OME) = 1 mcg/hr of a fentanyl patch.

So, if someone is on 50 mg total daily OME, you divide 50 by 2. That gives you about a 25 mcg/hr fent patch.

Fast Fact’s take: This is more aggressive than the label, and may be a good fit for younger, stronger patients.

One more consideration: time to effect.

Because of the delayed onset, many clinicians forget to use enough PRN opioids in the first 24 hours or so.

So, if someone is still in pain on day 1 of a fentanyl patch, the solution isn’t to increase the patch dose. It’s to provide rescue opioids until the patch kicks in.

PS: Want me to make a short video on this? 😉 Let me know.

See you next time,

SP

References:

Weissman DE, Rosielle DA. Converting to transdermal fentanyl. Palliative Care Network of Wisconsin. Published April 29, 2025. https://www.mypcnow.org/fast-fact/converting-to-transdermal-fentanyl/. Accessed August 17, 2025.

Disclaimer:

PainRx provides educational information for healthcare professionals, which is not intended as medical advice. Healthcare providers should exercise independent clinical judgment, consult up-to-date resources, and refer to official prescribing information before using any product, as new safety information may emerge.