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Letter to the editor: Subcutaneous sufentanil for palliative care patients in a hospital setting

Sir – Sufentanil is a highly lipophilic synthetic opioid analgesic. It is one of the anilinoperidone analogues in the same class as fentanyl, alfentanil and remifentanil. These ‘lipophilic opioids’ are more potent than morphine, have a more rapid onset of action and are shorter acting. Sufentanil is the most lipid soluble and most potent opioid in the class. It is normally delivered parenterally, or as a neuraxial analgesic,1 but can be delivered via the transmucosal and intranasal routes.2,3 Sufentanil has been used for breakthrough analgesia in palliative care,4 but there is limited data on its use by continuous subcutaneous infusion (CSCI).5 We describe our experience in the use of sufentanil delivered by CSCI to patients with advanced malignant disease in a hospital palliative care setting. Forty-eight patients who had received sufentanil over a three-year period were identified through hospital pharmacy records. Prior to starting sufentanil, all patients had been receiving other opioids, most commonly fentanyl or morphine. The most common reasons for switching to sufentanil were CSCI volume limitations, toxicity, renal impairment or inadequate pain control. The majority of patients had some degree of renal impairment at the time of opioid rotation to sufentanil. The effect on pain control following titration was generally described as favourable, but no formal efficacy or toxicity measures were undertaken. Many different drugs including clonazepam, cyclizine, glycopyrrolate, haloperidol, hyoscine, ketamine, methadone, methotrimeprazine, metoclopramide, midazolam and octreotide were used in combination with sufentanil with no incompatability observed. The starting dose of sufentanil ranged from 15 to 600 mcg/24 h (median 95 mcg/24 h). The dose of sufentanil was increased in 50%, decreased in 10% and remained the same in 38% patients. The median final dose was 130 mcg/24 h (range 15–700 mcg/24 h). Twenty patients (42%) received sufentanil until death and nine patients (19%) were discharged to another care setting on sufentanil. In the patients that remained in hospital, the median duration of sufentanil infusion was four days (range 1–14 days). The relative analgesic potency of sufentanil against other opioids has been assessed in a number of studies. Although generally said to be ~10 times more potent than fentanyl,1 other relative fentanyl: sufentanil ratios reported in the literature across a number of settings range from about 5:1 to 24:1.5,6 In this series, the median fentanyl: sufentanil conversion ratio in patients previously receiving fentanyl at the time of conversion was 10:1 (range 2.5:1–20:1). When all patients are considered and all opioids converted to fentanyl equivalent doses, the median conversion ratio was 11:1 (range 2.5–24:1). One ‘rule of thumb’ when switching from morphine to sufentanil is to give 50% of the total daily dose of oral morphine in mgs as sufentanil in mcgs (ie, 100 mg oral morphine/day would be converted to 50 mcg sufentanil given via a CSCI over 24 h). This equates to a fentanyl: sufentanil ratio of 13:1 and may be too conservative. Unlike many other opioids, the lipophilic opioids are not dependent on renal function for elimination and are probably less efficient at inhibiting bowel transit time than other opioids that are not as lipid soluble.7 It is usual practice on our unit to utilize these opioids in patients with bowel obstruction or abnormal renal function and/or within the context of opioid rotation. All the lipophilic opioids are known to accumulate in fat tissue. This results in delayed clearance of the drug following removal of a transdermal patch or discontinuation of an infusion. We therefore recommend caution when rotating from sufentanil to another opioid. An advantage of sufentanil is its relative potency in a concentrated volume. The dose of fentanyl that can be given via a CSCI is limited by dose/volume restrictions. Sufentanil offers a practical alternative to fentanyl at doses exceeding 750 mcg (ie, 15 mLs) when delivered over 24 h in a standard Graseby infusion device. Our experience has been that sufentanil is a useful opioid when considering opioid rotation, especially in patients with renal impairment. We have found it safe and effective to use in a syringe driver in combination with a number of other drugs commonly delivered by CSCI. This drug is more expensive than other opioids. We would recommend referral to specialist palliative care or pain teams rather than routine use by generalists.