NEWER NEUROMUSCULAR BLOCKING-AGENTS

Four neuromuscular blocking drugs, doxacurium, mivacurium, pipecuroniu m, and rocuronium have been or are about to be introduced into clinica l practice. The purpose of this MiniReview is to describe their pharma cology, to consider their place in clinical anaesthetic practice, and to examine whether the needs of the clinican have been met. Two of the agents (doxacurium, mivacurium) are benzylisoquinolines resembling at racurium and two (pipecuronium, rocuronium) are aminosteroids related to pancuronium and vecuronium. Two (doxacurium, pipecuronium) are long -acting compounds, similar in duration of action to pancuronium, altho ugh the need for such a profile is questionable. Rocuronium has an int ermediate duration of action and produces its maximum effect within tw o minutes which is much more rapid than any other non-depolarizing rel axant and this is probably a result of its poor potency. However, the onset of paralysis is not as quick as after succinylcholine. Mivacuriu m is unique because it is metabolized by plasma cholinesterase which p roduces a rapid recovery although slower than succinylcholine. All of the new drugs are devoid of serious cardiovascular or other side effec ts. The anaesthetist is now presented with an armamentarium of safe, n ondepolarizing muscle relaxants with Varying durations of action. Howe ver, the rapid onset, and recovery associated with succinylcholine are unique and important in the urgent control of a patient's airway and respiration. The indications for succinylcholine will not disappear an d the search for a non-polarizing replacement will continue.