Recent advances in neuromuscular blocking agents.

Since the introduction of (+)-tubocurarine into anaesthetic and surgical practice (1942), a number of non-depolarizing neuromuscular blocking agents (NMBs) with improved pharmacological properties have been developed during the last sixty years. However, after withdrawal of rapacuronium from clinical use, there is still a need for an ultra-short acting non-depolarizing muscle relaxant with rapid onset as substitution for the polarizing suxamethonium, which has several undesirable side-effects. In this paper, structure-activity relationships within four different series of NMBs (tetrahydroisoquinolinium, bistropinyl diester, aminosteroid, and amino peptide analogues) published in this millennium have been reviewed. The NMB properties of the most promising drug candidates from each series were discussed and compared to those of the already existing muscle relaxants.