Evaluation of neuromuscular and cardiovascular effects of two doses of rapacuronium (ORG 9487) versus mivacurium and succinylcholine

Background: This study compares the neuromuscular blocking and cardiovascul ar effects of rapacuronium (ORG 9487), a new aminosteroid nondepolarizing m uscle relaxant, to recommended intubating doses of succinylcholine and miva curium . Methods: Adult patients were randomized in an open-label fashion to receive 1-5 mu g/kg fentanyl before 1.5 mg/kg propofol induction followed by 1.5 o r 2.5 mg/kg rapacuronium, 1.0 mg/kg succinylcholine, or 0.25 mg/hg mivacuri um (i.e., 0.15 mg/kg followed by 0.1 mg/kg 30 s later). Results: Patient neuromuscular blockade status was monitored by measuring t he train-of-four response to a supramaximal stimulus at the ulnar nerve eve ry 12 s, Percentage of the first twitch of the train-of-four (T-1) at 60 s was similar in patients receiving 1.5 mg/kg rapacuronium, 2.5 mg/kg rapacur onium, and succinylcholine and was significantly less than in patients in t he mivacurium group (26, 16, and 18%, respectively, ns. 48%; P < 0.01), Tim es to 80% T-1 depression were also similar among patients in the 1.5 mg/kg rapacuronium, 2.5 mg/kg rapacuronium, and succinylcholine groups and signif icantly longer in the mivacurium group (62, 54, and 54 s, respectively, vs. 112 s; P < 0.01). Clinical duration was longer in all groups compared with the succinylcholine group; however, clinical duration in the 1.5 mg/kg rap acuronium group was shorter compared with the mivacurium group (15 vs. 21 m in, respectively; P < 0.01). Heart rate changes were mild in the 1.5 mg/kg rapacuronium, succinylcholine, and mivacurium groups. The patients iu the 2 .5 mg/kg rapacuronium group had significantly higher heart rates compared w ith patients in the mivacurium group. No differences were found in blood pr essure changes among patients in the four groups. Conclusions: Rapacuronium, 1.5 and 2.5 mg/kg, produced neuromuscular blocka de as rapidly as succinylcholine and significantly faster than mivacrurium Although succinylcholine continued to shaw the shortest duration, 1.5 mg/kg rapacuronium used a rapid onset and a relatively short duration and may be considered an alternative to succinylcholine.