SUBCUTANEOUS FENTANYL AND SUFENTANIL INFUSION SUBSTITUTION FOR MORPHINE INTOLERANCE IN CANCER PAIN MANAGEMENT

Eleven patients with cancer pain in a palliative care and chronic pain service required cessation of morphine due to unacceptable opioid sid e effects. In this retrospective study fentanyl was evaluated as a sec ond-line subcutaneously infused opioid. Starting doses ranged from 100 to 1000 mu g/24 h, and the duration of fentanyl infusion was 3-70 day s. The clinically derived mean relative potency of fentanyl to morphin e infusions was 68:1 (SD+/-23; range: 15-100), and we now recommend ca utious dose conversion at an approximate equivalence of 150-200 mu g f entanyl for 10 mg morphine in non-opioid naive chronic cancer pain pat ients. All patients demonstrated an improvement in the adverse effect( s) for which the change in opioid was undertaken. Adequate pain relief was achieved in all but 1 patient with mixed nociceptive and neuropat hic pelvic pain for whom an epidural infusion of a local anaesthetic/o pioid mixture was required. Fentanyl was changed to the more potent sy nthetic opioid sufentanil in 2 patients for whom the fentanyl dose nec essitated too large a volume for the portable syringe driver in use, T he clinically derived sufentanil to fentanyl relative potencies were 2 4:1 and 16:1, respectively. This achieved good analgesia and maintaine d the favourable side-effect profile seen with fentanyl. Subcutaneous infusion appears to be a safe and viable route of fentanyl delivery, a nd provided effective analgesia with a low incidence of adverse effect s in this small selected group of patients who were intolerant of subc utaneous morphine. We suggest a trial of subcutaneous fentanyl for sel ected patients who have intractable adverse effects on morphine, and i t is now the second-line infusable opioid in our service. Further pros pective evaluation of the role of these two synthetic mu opioid agonis ts in palliative care practice is warranted, as part of an evolving pi cture of variation in opioid side-effect profile seen with different d rugs within the class.