Fast Fact and Concept #2: Converting To-From Transdermal Fentanyl

Title: Fast Fact and Concept #2: Converting To-From Transdermal Fentanyl

Author(s): Weissman, D.

This Fast Fact and Concept is a brief outline of clinical information designed for attending physicians to use during teaching rounds or as the starting point for a conference.

Educational Objective(s)
Review key clinical aspects of terminal delirium.

Quick--what dose of Duragesic patch (Fentanyl transdermal) is equianalgesic to a 3 mg/hr morphine drip?

Conversions to and from Duragesic are notoriously tricky, requiring knowledge of the published conversion data, general opioid pharmacology and a generous dose of common sense. Here are the steps I recommended:

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 Duragesic - there are two methods:

METHOD 1. Look in the PDR, find the morphine conversion table, it says that 135-224 mg of morphine = 50 mcg patch. Note, this range of morphine is very broad; 50% of patients will be under-dosed when this conversion table is used.

METHOD 2. Use a ratio of MS:fentanyl of 100:1; 216mg/100/24hrs = 90 mcg/hr, can rounded to 75 mcg or 100 mcg patch

How to choose which dose?

A)Know that the "right" equianalgesic dose is likely to be somewhere close to or within the range of 50-100 mcg;

B) Know that for the elderly and anyone with renal impairment, the risk of sedation/respiratory depression with Duragesic is increased due to its long half-life, thus, choose the lower end of the dosing spectrum;

C) When in doubt, go low and slow, using prn breakthrough doses generously.

As a rule, all published opioid equianalgesic ratios should be thought of as a general reference guide to help avoid gross under or over dosing. Once chosen, the calculated dose is just a starting point for upward or downward dose titration.

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; Some patients need patch change every 48 hours.

The recommended upward dose titration interval is every 72 hours.

Place patches on non-irradiated, hairless skin. Data exists that Duragesica has less side effects than sustained release morphine.

References:

Physicians Desk Reference, 1999, pgs1418-1422.

Donner B, et al. Direct conversion from oral morphine to transdermal fentanyl. Pain 1996; 64:527-534.

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.

Disclaimer Concerning Medical Information:
Health care providers should exercise their own independent clinical judgment. Accordingly, the official prescribing information should be consulted before any product is used.

Contact: David E. Weissman, MD, FACP Editor, Journal of Palliative Medicine Palliative Care Program Director Medical College of Wisconsin (P) 414-805-4607 (F) 414-805-4608; dweissma@mail.mcw.edu

Copyright Notice: Users are free to download and distribute Fast Facts for educational purposes only. Citation for referencing: Weissman, D. Fast Fact and Concepts #02: Converting To-From Transdermal Fentanyl. May, 2000. End-of-Life Physician 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.

Creation Date: 1/2000

Format: Handouts

Purpose: Teaching

Audience(s)

Training: 1st/2nd Year Medical Students, 3rd/4th Year Medical Students, PGY1 (Interns), PGY2-6, Physicians in Practice

Specialty: Anesthesiology, Emergency Medicine, Family Medicine, General Internal Medicine, Geriatrics, Hematology/Oncology, Neurology, OB/GYN, Ophthalmology, Pulmonary/Critical Care, Pediatrics, Psychiatry, Surgery

Non-Physician: Nurses

ACGME Competencies: Medical Knowledge

Keyword(s): Adult, Chronic non-malignant pain, Pain treatment

The Fast Facts series is distributed for educational use only and does not constitute medical advice. For the most current version of Fast Facts visit the EPERC web site at www.eperc.mcw.edu. This mirror version is provided subject to copyright restrictions for educational use within the Inter-Instutional Collaborating Network on End-of-Life Care (IICN).