Blogs to Boards: Question 6

You visit a patient at home receiving hospice care for cancer. Her pain has been well controlled with long acting morphine 60mg BID and occasional PRN doses of short acting liquid morphine (10mg) over the past few weeks: she had been tolerating this well. She has had recent progressive functional decline and is currently at a PPS of 20%. In the last 24 hours the patient has vomited and has been more lethargic and having difficulty swallowing pills. She appears uncomfortable. In your examination you see a very thin patient who appears to be dying with a prognosis in the few days to a week range.

The patient’s son is a respiratory therapist at a hospital and is insisting you change the patient’s opioid to a fentanyl patch because “it is less sedating than morphine.”

The best response is:

  1. Because the patient is cachectic, you tell the family that fentanyl transdermal patches are not indicated because the medication will not be absorbed.
  2. Agree with the son and convert the patient to a 37.5mcg/hr fentanyl patch with oral morphine liquid 10mg q1 hour PRN
  3. Because the fentanyl will not be effective for over 24 hours, continue the long acting morphine sulfate 60mg BID but give it rectally instead of by mouth
  4. Suggest starting a morphine infusion via her port at 1.7mg/hr basal with a 3mg q30min bolus PRN after talking with the son about his concerns about sedation

Discussion: Correct answer is (d)

  1. Cachexia has not been show to be a CLINICALLY RELEVALANT factor in absorption of transdermal fentanyl.  Cachexia will decrease the amount of subcutaneous fat which is where fentanyl is stored AFTER absorption through the dermal layers. In 2009 Heiskanen did a study comparing blood levels between cachectic and non-cachectic volunteers and found no significant difference, although cachectic patients had a slightly lower mean concentration. There was no difference in VAS score.
  2. Fentanyl is not less sedating than morphine at equianalgesic doses.  Also there is no 37.5mcg/hr patch or 12.5mcg/hr patch. As written, and described by the manufacturer, the “12.5mcg/hr patch” is labeled and Rx’d as a “12mcg/hr” patch to prevent confusion with Rx’ing 125mcg/hr.  As for the conversion, it could be acceptable to use a 25mcg/hr &
       12mcg/hr patch (total 37mcg/hr) per the Fentanyl transdermal product insert. It recommends
       25mcg/hr for someone on OMDD of 60-134mg and 50mcg/hr for someone on OMDD 135-
       224, so this is right in the middle. The Breitbart/Donner conversion of 2mg morphine =
       1mcg/hr transdermal fentanyl which would be 60mcg/hr of fentanyl (You could choose 50 or
       75 depending on other clinical circumstances).
  3. The pharmacokinetics of fentanyl do not warrant switching to it if otherwise indicated. Morphine still has time to circulate and get out of her system, and fentanyl begins to reach significant blood concentrations 8-12 hours after application.  If needed, she can be bridged with a few doses of liquid morphine. In addition, people do not prefer rectal administration if it could be avoided.
  4. A morphine continuous infusion allows for the continuation of the current effective opioid in a patient who is likely not going to regain swallowing function.  The conversion is most direct (120mg OMDD = 40mg daily IV = 1.7mg/hr (1.5 if your pumps are limited in decimal rates). A 3 mg IV morphine bolus most closely replicates the 10mg oral morphine doses that were effective prior. If you did not choose this answer because your hospice doesn’t use continuous infusions (expense, nurse familiarity, not available from local pharmacy) then start talking with your hospice to decrease these barriers to an effective and essential tool to good pain management.


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