ORG-9487 NEUROMUSCULAR BLOCK AT THE ADDUCTOR POLLICIS AND THE LARYNGEAL ADDUCTOR MUSCLES IN HUMANS

Background: ORG 9487 is a new steroidal nondepolarizing muscle relaxan t with a rapid onset of action, This study was designed rep determine the neuromuscular blocking profile of ORG 9487 at the adductor muscles of the larynx and. the adductor pollicis. Methods: In 30 adults, anes thesia was induced with propofol (2-5 mg/kg) and fentanyl (2-3 mu g/kg ). After train-of-four stimulation, the block of the laryngeal adducto r muscles was evaluated by measuring the pressure changes in the cuff of the tracheal tube placed between the vocal cords, and the force of the contraction of the adductor pollicis was measured with a force tra nsducer. Patients were randomly allocated to receive ORG 9487 at intra venous bolus doses of 0.75, 1.5 or 2 mg/g (n = 10 in each group). Resu lts: Time to peak effect nas significantly shorter at the vocal cords than at the adductor pollicis muscle (P < 0.001). Onset time at the vo cal cords was 62 +/- 16 s, 62 +/- 13 s, and 52 +/- 14 s (mean +/- SD) after doses of 0.75, 1.5, and 2 mg/kg, respectively (not significant). Onset time at the adductor pollicis muscle was 126 +/- 33 s, 96 +/- 2 0 s, and 82 +/- 21 s after 0.75, 1.5, and 2 mg/kg doses, respectively (P < 0.001). Maximum block was significantly less intense at tile voca l cords than at the adductor pollicis muscle (69 +/- 15% vs. 94 +/- 4% after 0.75 mg/kg; 86 +/- 7% vs. 97 +/- 4% after 1.5 mg/kg; and 91 +/- 5% vs. 99 +/- 1% after 2 mg/kg). After 1.5 mg/kg duration to 25%, rec overy was 3.7 +/- 2.2 versus 10.2 +/- 2.5 min at the vocal cords and t he adductor pollicis muscle, respectively and 75% recovery occurred at 9.7 +/- 3.7 min at the vocal cords and at 18.3 +/- 5.2 min at the add uctor pollicis muscle.Conclusions: ORG 9487 has a rapid onset of actio n at the laryngeal adductor and the adductor pollicis muscles. Onset a nd duration of action are faster at the vocal cords than at the adduct or pollicis muscle. However, the maximum block obtained at the larynge al muscles was less than at the adductor pollicis, regardless of the d ose of ORG 9487.