Administration of clinical doses of neostigmine, commonly used in anaesthesia, and assessment of its effects on muscle strength, using a dynamometer, in healthy awake volunteers.

Neostigmine is an anticholinesterase agent that is commonly used in anesthesia to reverse non-depolarizing neuromuscular blocking agents (NMBA). It is used to improve the rate of recovery from moderate non-depolarizing neuromuscular blockade and reduce the incidence of residual blockade. Neostigmine increases acetylcholine levels at the neuromuscular junction by inhibiting the breakdown of acetylcholine (Ach), which competitively antagonizes the NMBA. Neostigmine also acts at muscarinic sites leading to unwanted cholinergic side effects. Therefore the anti-muscarinic agents glycopyrrolate or atropine are administered in conjunction with neostigmine to reduce the severity of the effects. Clinical doses of neostigmine have been reported to cause muscle weakness when administered after full recovery from blockade. However, these reports are potentially confounded by the presence of other anesthetic agents also known to influence neuromuscular blockade.Without the use of quantitative neuromuscular function monitoring, patients who have spontaneously recovered from NMBAs may be given neostigmine unnecessarily. The primary aim of this study is to determine if clinical doses of neostigmine administered to healthy, unanesthetized volunteers would cause muscle weakness and impair respiratory function. We sought to define the size of the effect with hand grip strength, electromyography and spirometry. The secondary aim was to record the signs and symptoms experienced by the participants.