Fast Fact and Concept #002; Converting To-From Transdermal Fentanyl

2nd Edition

Author(s): Weissman, D.

Quick --what dose of Duragesic patch (Fentanyl transdermal) is equianalgesic to a 3 mg/hr morphine continuous infusion?
Conversions to and from Fentanyl transdermal are notoriously tricky, requiring knowledge of the published conversion data, general opioid pharmacology and a generous dose of common sense.

Step 1. Calculate the 24 hr morphine dose: 3 mg x 24 = 72 mg IV morphine/24 hrs;

Step 2. Convert IV to oral morphine: at a ratio of 1 mg IV = 3 mg oral; thus 72 mg IV = 216 mg po/24 hours;

Step 3. Convert the oral morphine dose to Duragesicâ-there are two methods:

Key Considerations

1. All equianalgesic ratios/formulas are approximations; clinical judgment is needed when making dose or drug conversions.

2. The risk of sedation/respiratory depression with fentanyl transdermal is probably increased in the elderly or patients with renal impairment due to its long half-life, thus, choose the lower end of the dosing spectrum.

3. When in doubt, go low and slow, using prn breakthrough doses generously while finding the optimal dosage

Other teaching points about Duragesic:

• Start at the lowest dose, 25 mcg in an opioid naïve patient; there is no maximum dose.
• Therapeutic blood levels are not reached for 13-24 hours after patch application and drug will be continue to be released into the blood for at least 24 hours after patch removal.
• Opioid withdrawal symptoms can occur during dose conversions—care must be taken to avoid this by use of breakthrough opioids or other dosing systems.
• Some patients will need to have their patches changed every 48 hours.
• The recommended upward dose titration interval is no more frequently than every 72 hours.
• Place patches on non-irradiated, hairless skin.
• Direct heat applied over the patch can increase drug absorption with increased toxic effects.
• There is no data that cachectic patients have reduced efficacy due to loss of subcutaneous fat

See Fast Fact #36: Calculating opioid dose conversions.

References:

1. Physicians Desk Reference, 2005
2. Donner B, et al. Direct conversion from oral morphine to transdermal fentanyl. Pain 1996; 64:527-534.
3. Payne R, et al. QOL and cancer pain: satisfaction and side effects with Transdermal fentanyl versus oral morphine. J Clinical Oncology 1998:16:1588-1593.
4. Breitbart W. An alternative algorightm for dosing transdermal fentanyl for cancer-related pain. Oncology 2000; 14:695-702.
5. Gourlay GK. Treatment of cancer pain with transdermal fentanyl. The Lancet Oncology 2001; 2:165-172.

Fast Facts were edited by David Weissman MD, Palliative Care Center, Medical College of Wisconsin until January 2007.  For comments/questions write to the current editor, Drew Rosielle MD: drosiell@mcw.edu. The complete set of Fast Facts is available at EPERC: www.eperc.mcw.edu

 Copyright/Referencing Information : Users are free to download and distribute Fast Facts for educational purposes only. Citation for referencing: Weissman DE. Converting To/From Transdermal Fentanyl, 2 nd Ed. Fast Fact and Concept #2: July 2005. End-of-Life Palliative Education Resource Center www.eperc.mcw.edu.

Disclaimer: Fast Facts provide educational information, this information is not medical advice. Health care providers should exercise their own independent clinical judgment. Some Fast Fact information cites the use of a product in dosage, for an indication, or in a manner other than that recommended in the product labeling. Accordingly, the official prescribing information should be consulted before any such product is used.

Purpose: Teaching

Audience(s)

ACGME Competencies: Medical Knowledge

Keyword(s): Pain>opioids