Potency Determination for Vecuronium (ORG NC45)

Abstract

To compare 2 methods of estimating the potency of neuromuscular relaxants of medium duration, the potency of vercuronium (ORG NC45) was determined using cumulative dose-response (CDR) techniques. These data were compared with values obtained using the single bolus technique. During 60% N2O-halothane anesthesia, patients received 10 .mu.g/kg vecuronium; additional incremental doses of vecuronium, 5 .mu.g/kg, were given when no change occurred in the height of 3 successive twitches. Using these dose-response data, least-squares regression lines and ED20, ED50 and ED80 were determined. These results were compared to values obtained by the single bolus technique under comparable conditions. The CDR and single bolus technique yielded ED50 values of 19.9 and 15.0 .mu.g/kg, respectively. All potency estimates by CDR were larger than those obtained by the single bolus dose technique. For vecuronium, a medium duration neuromuscular relaxant, CDR yields potency estimates which are larger than those obtained by the traditional single bolus dose technique. Because the single bolus dose technique is the accepted method for construction of dose-response curves, CDR should probably not be used for potency determination of muscle relaxants of medium and short duration such as vecuronium.