Transdermal fentanyl to parenteral morphine route switch and drug rotation in refractory cancer cachexia

Abstract

It is recommended not to use transdermal fentanyl (Fe) patches (TFP) in cancer cachexia but TFP may be the only available option for pain. Limited evidence suggests lower Fe absorption from TFP in cachexia. We describe a case of metastatic breast cancer with refractory cachexia. Her pain was uncontrolled on TFP and was route switched and drug rotated to intravenous morphine (M). We were conservative and did not use the 1:100 TFP to oral M conversion ratio. Assuming opioid needs were similar before and after switch/rotation, the suitable conversion ratio in this case was about 1:25. Absent clear guidelines on converting from TFP in cachexia, it is better to avoid TFP. When essential to use TFP in cachexia, caution should be taken when switching from TFP to avoid overdose.

Transdermal fentanyl patch provides better pain relief and faster functional recovery after total knee arthroplasty:a meta-analysis

“…Although these patches release the drug via the skin at a steady rate, the subsequent plasma level and clearance resemble the intravenous fentanyl (7). The blood concentration of fentanyl through transdermal method was equal to that of intravenous method after 8-12 h, and at least remained steady over 72 h till the patch was worn (8). If TFP was applied 12-14 h before surgery, it would powerfully and durably relieve postoperative acute and subacute pain after TKA (9).…”