Modern medicine is pushing away from opioid-based pain management through different innovative approaches. That being said, opioids are still sometimes necessary due to their potent effects. Both remifentanil and fentanyl, two synthetic drugs, represent strong opioid-based analgesic solutions. Remifentanil and fentanyl are related formulations but have significant differences.
Remifentanil is chemically related to fentanyl and has similar pharmacodynamic properties, with a rapid onset of action. However, it is slightly more potent than fentanyl. Remifentanil is also unique in that its metabolism is independent of organ function 1.
Researchers have long investigated the clinical differences between remifentanil and fentanyl. One study seeking to compare the use of remifentanil and fentanyl during elective supratentorial craniotomy for space-occupying lesions identified that their induction hemodynamics were similar. Intracranial pressure and cerebral perfusion pressure were also similar, as was the median time to tracheal extubation, and the incidence of nausea and vomiting. However, isoflurane use was found to be greater in the patients who received fentanyl, as was systolic blood pressure. Furthermore, while no patient receiving remifentanil required naloxone, which can quickly reverse a too-high dose of opioids, seven patients receiving fentanyl needed it. In the end, the researchers concluded that remifentanil may be a reasonable alternative to fentanyl in the context of elective supratentorial craniotomy.
Another study sought to assess the effects of three different opioid approaches for cardiac surgery on postoperative pain, time to extubation, time to intensive care unit discharge, time to hospital discharge, and cost. Data analyses demonstrated that the more expensive but shorter-acting opioids, including remifentanil, produced equally rapid extubation, similar stays, and similar costs to fentanyl—indicating that any of these opioids may be recommended for fast-track cardiac surgery 2.
Finally, a randomized, double-blind study sought to probe the analgesic efficacy and side effects of continuous constant-dose infusions of remifentanil following total abdominal hysterectomy, comparing it to fentanyl 3. Data failed to reveal any significant differences in visual analogue scale scores of pain, time to first postoperative analgesics, or additional analgesics between the two groups. In particular, the incidences and severities of postoperative nausea and vomiting and opioid related side effects were no different across the groups. The researchers concluded that the continuous infusion technique of remifentanil was not superior compared to fentanyl.
Research has also shown, however, that there are clinical differences among various opioids, including remifentanil and fentanyl in particular. One study found clear, statistically significant differences among remifentanil and fentanyl in terms of the bispectral index and effect-site concentration in the different study groups 4.
More recently though, a double-blind, randomized, multicenter study was conducted to compare the efficacy and safety of remifentanil and fentanyl for intensive care unit sedation and analgesia 5. Analgesia-based sedation with remifentanil titrated to response was demonstrated to provide effective sedation and rapid extubation without the need for propofol in most individuals. Fentanyl was similar, likely because the dosing algorithm required frequent monitoring and adjustment, thereby preventing over-sedation. However, the rapid offset of analgesia with remifentanil resulted in a greater incidence of pain, highlighting the need for proactive pain management when transitioning to longer acting analgesics.
References
1. Simmons, B. & Kuo, A. Analgesics, Tranquilizers, and Sedatives. Card. Intensive Care 421–431.e5 (2019). doi:10.1016/B978-0-323-52993-8.00040-0
2. Engoren, M., Luther, G. & Fenn-Buderer, N. A comparison of fentanyl, sufentanil, and remifentanil for fast-track cardiac anesthesia. Anesth. Analg. (2001). doi:10.1097/00000539-200110000-00011
3. Choi, S. H. et al. Comparison of Remifentanil and Fentanyl for Postoperative Pain Control after Abdominal Hysterectomy. Yonsei Med. J. 49, 204 (2008). doi: 10.3349/ymj.2008.49.2.204
4. Lysakowski, C., Dumont, L., Pellégrini, M., Clerque, F. & Tassonyi, E. Effects of fentanyl, alfentanil, remifentanil and sufentanil on loss of consciousness and bispectral index during propofol induction of anaesthesia. Br. J. Anaesth. (2001). doi:10.1093/bja/86.4.523
5. Muellejans, B. et al. Remifentanil versus fentanyl for analgesia based sedation to provide patient comfort in the intensive care unit: a randomized, double-blind controlled trial [ISRCTN43755713]. Crit. Care 8, R1 (2004). doi: 10.1186/cc2398