The timing of administration may be an important factor in order to obtain maximal antagonizing effect of anticholinesterase on neuromuscular blockade. The objective of this study is to seek for the optimal administration time of pyridostigmine for reducing the recovery time of vecuronium.

Thirty patients were devided into three groups,who were receiving intravenously pyridostigmine (0.2 mg/kg) at 10% (group 1), 20% (group 2) and 25% (group 3) recovery of T1. The recovery indices (RI: time taken for T1 to recover from 25 to 75% of control) and recovery time (time taken for T1 to recover from 5% to 20, 25, 50 & 75%) in vecuronium (0.1 mg/kg) neuromuscular blockade were checked and compared between 3 groups using train of four stimulation with Relaxograph(Datex co., Finland).

The recovery time (T5-20, T5-25, T5-50, T5-75) was significantly faster in the group 1 than the group 3. But there were no significant differences in recovery indices (RI) between 3 groups.

Provided there is a slightest evidence of spontaneous recovery, early administration of anticholinesterse will reduce the recovery time of nondepolarizing neuromuscular block. But it can not affect the dissociation rate of vecuronium (KD) and there were no significant differences in recovery indices.