A comparison of the remifentanil and fentanyl adverse effect profile in a multicenter phase IV study

Study Objective: To compare the frequency of adverse effects of remifentanil and fentanyl in a large and diverse patient population. Design: Prospective, randomized, open-label study. Setting: Multicenter study including academic and community hospitals. Patients: 2,438 adult patients (1,496 outpatients and 942 inpatients) scheduled for elective surgical procedures under general endotracheal anesthesia of at least 30-minute duration. Interventions: Patients were randomly assigned to receive either intravenous (IV) remifentanil (n = 1,229) 0.5 μg/kg/min for induction and tracheal intubation followed by an infusion rate of 0.25 μg/kg/min or fentanyl (n = 1,209) administered according to the anesthesiologist's usual practice. Anesthesia was maintained with propofol and/or isoflurane (with or without nitrous oxide) titrated according to protocol. Transition analgesia with either morphine or fentanyl was administered in the remifentanil and, at the anesthesiologist's discretion, in the fentanyl group. Measurements: The overall nonspecific and specific (i.e., opioid-related) adverse effects were recorded. Main Results: Remifentanil was associated with more intraoperative hypotension than fentanyl (p< 0.05). All four cases (0.3%) of muscle rigidity occurred in the remifentanil-treated outpatients. There were no significant differences between the two drugs with respect to other adverse events (i.e., episodes of hypertension, bradycardia, respiratory depression, and apnea). Conclusions: In the doses used, both remifentanil and fentanyl have a similar frequency of adverse effects except for the higher frequency of hypotension associated with the use of remifentanil.