EFFECTS OF CHOLINESTERASE-INHIBITORS ON THE NEUROMUSCULAR BLOCKING ACTION OF SUXAMETHONIUM

Prolonged neuromuscular block occurs when suxamethonium is given after neostigmine or pyridostigmine; however, studies of edrophonium and su xamethonium have yielded conflicting results. We have studied, therefo re, interactions between suxamethonium and all three anticholinesteras es in rats anaesthetized with pentobarbitone. After recovery from an i nitial bolus of suxamethonium, saline, edrophonium, pyridostigmine or neostigmine was administered and a second dose of suxamethonium was th en given. All three anticholinesterases prolonged the duration of neur omuscular block (90% suppression to 50% twitch recovery) to 127 (SEM 9 )%, 127 (10)% and 138 (11)% of baseline for edrophonium, pyridostigmin e and neostigmine, respectively. Recovery index (25% to 75% Switch rec overy) was increased also to 125 (9)%; 149 (10%) and 185 (15)% of base line, respectively for the three drugs.