Dose-ranging study in younger adult and elderly patients of ORG 9487, a new, rapid-onset, short-duration muscle relaxant

The purpose of this multicenter, randomized, assessor-blind placebo-controlled study was to determine which of five doses of the new, rapid-onset neuromuscular relaxant, ORG 9487, provided both good to excellent tracheal intubating conditions 60 s after administration and a clinical duration of action <20 min in 120 younger (aged 18-64 yr) and 61 elderly (aged 65-85 yr) adult patients. Anesthesia was induced with fentanyl (2-5 mu g/kg) and thiopental (3-6 mg/kg) and maintained with N2O/O-2 and a propofol infusion (50-300 mu g.kg(-1).min(-1)). Neuromuscular train-of-four (TOF) monitoring by electromyography (Datex Relaxograph) commenced immediately after anesthetic induction and was followed, within 30 s, by one of five doses of ORG 9487 (0.5, 1.0, 1.5, 2.0, 2.5 mg/kg) or a placebo. Tracheal intubation was attempted at 60 s and again, in the case of failure, at 90 s. Conditions were assessed with a 4-point scale. Maximum block, clinical duration (time to 25% T1 recovery), and recovery (TOF greater than or equal to 0.7) were measured. Dose-dependent changes were observed in tracheal intubating conditions and neuromuscular block. Good to excellent intubating conditions at 60 s were present in most younger adult (52 of 60) and elderly (26 of 31) patients administered doses greater than or equal to 1.5 mg/kg. Mean clinical durations <20 min were observed in adult patients at doses up to 2.0 mg/kg and in geriatric patients up to 1.5 mg/kg. Thus, doses of 1.5-2.0 mg/kg ORG 9487 enabled both rapid tracheal intubation and a short clinical duration of action in adult and elderly patients.