Puzzling Pain

Thank you for joining me again. This month I am discussing Puzzling Pain. I am starting with this rather technical subject because Symptom Management is at the core of our care for patients with cancer. When our patients are in pain, it is difficult to explore any other areas of distress: psychological, spiritual/existential, or emotional.

As you can imagine, I’m only consulted when the usual strategies to manage cancer-related pain are no longer working. You’ve already escalated the long-acting morphine or oxycodone, added short acting opioids and adjuvants (e.g., gabapentin or pregabalin for the patients with neuropathic pain, NSAIDs for bone pain) and yet they’re still in severe pain. So, let’s look at a typical puzzling case. 

The fentanyl “vest”
Mr. Rowan was a 56-year-old man with locally recurrent, advanced head and neck cancer.  He had resisted a feeding tube, and so had lost about 30 pounds in the months before I met him. When I saw him in clinic, he had a J tube for nutrition and medications, but he was cachectic and in severe pain. He rated it at 15/10, burning, aching, and shooting through his jaw. His oncologist had started him on a fentanyl patch and prn liquid hydromorphone and had increased the number of patches several times to try to relieve Mr. Rowan’s pain. He was no longer able to take gabapentin capsules.

On exam, Mr. Rowan had six, 25 ug/hr fentanyl patches placed over his upper back and upper chest, as well as two on the volar sides of his upper arms (total of 200 ug/hr).  A fentanyl “vest”! The oncologist had chosen small dose patches because of their small size and ease of placement on his thin arms and bony chest. But there had been NO change in the amount of prn hydromorphone Mr. Rowan used, which was 8 mg po every three hours (he set his phone alarm to let him know when he could take the next dose). Why no change? As you’ve guessed by now, the fentanyl patches were ineffective, and Mr. Rowan remained in pain.

Why didn’t they work? Fentanyl patches don’t work in cachectic patients. Fentanyl patches are just drug delivery systems that create subcutaneous reservoirs of fentanyl in fat. Without a fat reservoir, the fentanyl goes into what little fat is in the subcutaneous tissue; it’s then transported by the blood to the liver, and immediately metabolized. No blood level results, and so no pain relief.

How about methadone?
I knew we needed to remove his “vest”, but what next? I couldn’t use sustained release morphine, oxycodone, or hydromorphone because he had a feeding tube and those pills can’t be crushed. I could have used IR liquids q4h, but that’s pretty inconvenient, and I couldn’t add neuropathic adjuvants for the component of his pain that was neuropathic.

Mr. Rowan needed continuous relief from a medication that would treat the neuropathic component of his pain and be deliverable through the J tube. The answer was: liquid methadone, either as a preparation in itself, or as tablets that are crushed and completely dissolved in water. 

What methadone dose should I start with?
There is a safe method for changing patients from one opioid to another, using what is called the Oral Morphine Equivalent (OME).

Before I could determine the methadone dose, I needed to convert the amount of hydromorphone he took in the past day to the OME, and I could then use the table below to determine the starting dose of the methadone. (N.B. I didn’t feel Mr. Rowan was receiving any pain relief from the fentanyl patches, so I used only the amount of oral hydromorphone he took in the past day to calculate the OME.)

Going forward, as we continue on this journey of making palliative care for patients with cancer more widely accessible, we will address many more topics under the umbrella of Pain & Symptom Management, as well as highly relevant topics in Communications with Patients and Families, Special Topics (including navigating faith, issues of particular concern to the LGBTQ+ community, working with medical translators, and much more), and effectively and compassionately partnering through End of Life & Bereavement.

Please do visit my website janetabrahm.com or or email me directly with any questions, or thoughts on future topics to address.

Thank you again for being here.

Best,
Janet Abrahm, M.D.

Posted on: December 12, 2024