Neuromuscular Blocking

Abstract

Neuromuscular blocking drugs (NMBDs) have become an established part of anaesthetic practice since Griffith and Johnson in Montreal first described the use of curare to facilitate muscle relaxation in a healthy man undergoing an appendicectomy in 1942....

Depolarizing NMBDs

Mechanism of action

Depolarizing drugs are agonists at ACh receptors. Succinylcholine is the only depolarizing NMBD in clinical use. It is effectively two ACh molecules joined through the acetate methyl groups. The two quaternary ammonium radicals bind to the two α-subunits of one nicotinic receptor, and depolarization occurs. When voltage-sensitive sodium channels sense membrane depolarization (as a result of activation of the ACh receptors), they first open (Fig. 1A(b)) and thereafter close and become inactivated (Fig. 1A(c)). The membrane potential must be reset before the sodium channels can be reactivated (Fig. 1A(a)). This is a very rapid process with ACh (1 ms), as it is hydrolysed by acetylcholinesterase (AChE) within the synaptic cleft...