Fentanyl Transdermal Conversion Case Study

RL is a 64 y/o female with breast cancer metastatic to brain, bones, and spine. RL has experienced significant weight loss over the past month and her family reports recent episodes of confusion. RL is now exhibiting signs of uncontrolled pain that had been previously well controlled. RL lives alone and admits to forgetting to take her medications. Family members regularly visit a few times each week to assist with ADLs. RL’s doctor has asked for a recommendation for transdermal fentanyl (TDF) to improve medication compliance and to better control her pain.

Current pain medications:

  • Morphine SR 100mg PO Q8H
  • Morphine 20mg/mL; 1ml (20mg) PO Q4H PRN (number of doses per day not known)

Recommendation listed in steps:

  1. Assessment: Uncontrolled pain, poor medication adherence due to impaired cognition, cachexia and lack of around the clock caregivers
  2. Total Daily Usage of Current Opioids: Morphine PO 300mg/day that, until recently, controlled her pain well.
  3. New Opioid Requested: Transdermal Fentanyl (TDF)
  4. New Dose and Interval: Using standard conversion table (example below), 300mg/day of Morphine is equivalent to 125mcg/hr of Fentanyl. Considering patient has not been compliant recently, in addition to recent weight loss indicating cachexia, reducing the dose to a 100mcg patch applied topically every 72 hours and assess response is recommended. Maintain current breakthrough regimen with Morphine concentrate. Fentanyl Transdermal Conversion Case Study
  5. Monitor for therapeutic effectiveness (pain severity rating, breakthrough doses used) and toxicity (increased sedation or confusion, difficulty arousing patient).
  6. Titrate dose after 3-6 days. Note: more frequent dose increases may result in adverse effects/overdose.

Use of Transdermal Fentanyl (TDF) in Cachectic, Debilitated Patients and its Effect on Absorption:

  • A 2009 study by Heiskanen and colleagues found that cachectic patients required significantly higher doses of TDF to produce pain relief compared to patients of normal weight, despite cachectic patients having lower plasma concentrations of fentanyl. However, no additional evidence has been published to support these findings. Considering how TDF is absorbed, in theory, it makes sense that less subcutaneous fat on a patient would result in less TDF absorbed. However, clinically, effects vary and are entirely patient-specific.
  • Although a conversion ratio that adjusts for cachectic patients is no longer used at Enclara Pharmacia, dose reduction when TDF therapy is initiated is often considered along with recommendations to monitor and titrate patient’s dose slowly. Per manufacturer’s instruction, “life-threatening respiratory depression is more likely to occur in elderly, cachectic, or debilitated patients as they may have altered pharmacokinetics or altered clearance compared to younger, healthier patients. Monitor such patients closely, particularly when initiating and titrating [TDF] and when [TDF] is given concomitantly with other drugs that depress respiration.”

TDF Considerations in Hospice/Palliative care:

  • TDF is indicated for the management of pain in opioid-tolerant patients, severe enough to require daily, around-the-clock, long-term opioid treatment and for whom alternative treatment options are inadequate.
  • Cachexia or involuntary weight loss is characterized by a decrease in fat and skeletal muscle mass as a result of underlying illness. Unintentional weight loss/cachexia is associated with an increase in mortality. Cachexia occurs with increased prevalence in patients with cancer.

For additional information on this topic, please review these references:

  • Enclara Pharmacia’s On Demand Educational Webinar, “Medication Calculations, Opioid Conversions and Titration: A Practice Review”. Click here; Enclara Portal to log in.
  • Heiskanen T, Matzke S, Haakana S et al. Transdermal fentanyl in cachectic cancer patients. Pain. 2009; 144:218-22.
  • Mercadante S, Caraceni A. Conversion ratios for opioid switching in the treatment of cancer pain: a systematic review. Palliative Medicine. 2011; 25(5): 504-515.