Effects of Neostigmine and Pyridostigmine on Duration of Succinylcholine Action and Pseudocholinesterase Activity

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Abstract
Effects of the anticholinesterase drugs on the duration of action of succinylcholine (SCh) and pseudocholinesterase activity were studied in 16 adult patients undergoing general anesthesia. Each patient received 2 doses of SCh, 1 mg/kg, i.v., the 1st dose was given before and the 2nd dose, 5 min after neostigmine, 5 mg, or pyridostigmine, 25 mg. Electromyographic determinations were used to measure the duration of SCh-induced block. Prolongation in the neostigmine group (n = 8) was compared with that in the pyridostigmine group (n = 8). Pseudocholinesterase activities were determined before, during and at the point of full recovery of neuromuscular blockade by the 2nd dose of SCh. The effect of SCh, 1 mg/kg, was significantly prolonged from the control value, 11.1 .+-. 1.43 (mean .+-. SE), to 35 .+-. 3.24 min following neostigmine and from 13.1 .+-. 1.45 to 23.9 .+-. 2.5 min after pyridostigmine. Pseudocholinesterase activities determined 5 min after administration of neostigmine and pyridostigmine decreased to 21 and 20% of control, respectively. Full recovery from the SCh-induced block was observed; enzymatic activities remained suppressed to 47 and 39% of control in the neostigmine and pyridostigmine groups, respectively. The neuromuscular blocking effect of SCh was significantly prolonged by both neostigmine and pyridostigmine, but more by neostigmine. The enzyme might not be the sole factor determining the effect of anticholinesterase drugs on the duration of action of SCh.

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