Comparison of vecuronium with ORG 9487 and their interaction

Abstract

Purpose: To compare the pharmacodynamic behaviour of vecuronium with that of ORG 9487, we measured the time-course of action of equipotent doses of ORG 9487 and vecuronium and investigated their mutual interaction when given in succession. Methods: Sixty ASA I-II patients were anaesthetized with thiopentone, fentanyl, halothane and nitrous oxide and assigned randomly to four groups. Each patient received an initial dose (ID) of either vecuronium (V) or ORG 9487 (O) followed by maintenance doses (MD(n)) of either V or O (ID/MD; O/O, V/O, O/V, and V/V). The time course of action was measured mechanomyographically, determining the duration until 25% recovery of the single twitch (DUR25). Results: The onset time of an ID of ORG 9487 was shorter than that of an ID of vecuronium (96 vs 203 sec, P < 0.001). The DUR25 of the ID of ORG 9487 was less than half that of vecuronium (10.7 ± 2.8 vs 28.8 ± 6.1 min, P < 0.001). The DUR25 of MD1 and MD2 of ORG 9487 were shorter than those of vecuronium (O/O; 7.3 ± 2.8 and 8.5 ± 2.4 min; V/O: 12.7 ± 3.3 and 11.5 ± 3.5 min, vs O/V: 16.4 ± 4.5 and 20.6 ± 4.7 min; V/V: 18.8 ± 3.0 and 20.1 ± 3.8 min, respectively, P < 0.05). An ID of vecuronium prolonged the DUR25 of MD1 and MD2 of ORG 9487 (P < 0.05). Conclusion: ORG 9487 is a muscle relaxant with a shorter duration of action than vecuronium. Maintenance doses of ORG 9487 are also shorter acting than roughly equipotent maintenance doses of vecuronium, irrespective of which relaxant is given initially.