ANTAGONISM OF ATRACURIUM-INDUCED NEUROMUSCULAR BLOCKADE BY NEOSTIGMINE OR EDROPHONIUM

Antagonism of atracurium-induced neuromuscular blockade by neostigmineor edrophonium has been studied using the tetanic (50 Hz) andtrain-of-four (2 Hz) or single twitch responses of the adductorpollicis muscle in 22 anaesthetized patients. A further ninepatients not given an anticholinesterase acted as a controlgroup. In two groups (six patients for each anticholinesterase)in whom antagonism was attempted at 95–98% blockade ofthe tetanic response, recovery of the tetanic response aftertwo or three doses of edrophonium 0.75 mg kg^–1 i.v. wasnot statistically different from that in the control group;recovery after two doses of neostigmine 2.5 mg i.v. was significantlyfaster (P < 0.001). Recovery of the single twitch responseafter antagonism with edrophonium, although longer than thatwith neostigmine (P < 0.01), was significantly shorter thanin the control group (P < 0.05). When edrophonium is givenat the commencement of recovery, the initial rapid antagonismof tetanic block is not sustained, whereas antagonism by neostigmineis more persistent and the recovery phase is significantly shortened.In a further two groups of patients (n = 5) given atracurium0.3 mg kg^–1 i.v. antagonism was not attempted until thepeak height of the tetanic contraction had reached approximately50% of the control value. It was found that recovery of thetetanic and train-of-four responses was significantly faster(P < 0.05–0.001) after antagonism with edrophonium0.75 mg kg^–1 i.v. than with neostigmine 2.5mg i.v. (approx.0.04 mg kg^–1). The train-of-four response recovered moreslowly than did the tetanic response after both agents (P <0.05–0.01). Department of Anaesthetics, University College Hospital, LondonWC1.^*Clinical Investigation Department, Clinical and Applied researchDivision, The Wellcome Research Laboratories, Beckenham, Kent.