SOME EFFECTS OF DIISOPROPYL PHENOL (ICI 35 868) ON THE PHARMACODYNAMICS OF ATRACURIUM AND VECURONIUM IN ANAESTHETIZED MAN

The effects of a bolus injection of diisopropyl phenol 2 mgkg–1 i.v. and an infusion (150 µg kg–1 min–1for 30 min and 75 µg kg–1 min–l thereafter)on the pharmacodynamics and dose-response curves of atracuriumand vecuronium were studied in 52 healthy (ASA I or II) patients.Under anaesthesia with diisopropyl phenol, the cumulative dose-responsecurves of both myoneural blocking drugs were shifted to theleft when compared with previously reported results. However,there was no clinically significant change in the pharmacodynamicsof either drug after the bolus injection of the blocking drug.Diisopropyl phenol 2 mg kg–1 i.v. administered duringsteady-state infusions of vecuronium and atracurium increasedthe depth of the constant neuromuscular blockade. When diisopropylphenol alone was given to four patients there was no changein the twitch height. These results show that diisopropyl phenol,given according to the regimen in this study, potentiates bothof the neuromuscular blockers studied but does not prolong theduration of action of either drug. During the infusion of diisopropylphenol, vecuronium was found to be five times more potent, tohave a more rapid onset time, and to be shorter acting thanan equipotent dose of atracurium. ^*Present address: Department of Anaesthesia, Royal Infirmary,Glasgow