Curare and its successors.
A 50-year's evolution

by
Buzello W, Diefenbach C.
Institut fur Anasthesiologie
und Operative Intensivmedizin,
Universitat zu Koln.
Anasthesiol Intensivmed Notfallmed Schmerzther. 1992 Aug;27(5):290-9


ABSTRACT

The introduction of curare into clinical anaesthesia by Griffith and Johnson in 1942 contributed to the termination of the era where anaesthesia was a reversible intoxication rather than the result of controlled drug action. Curare allowed general anaesthesia to be reduced to a lighter level, thereby conferring a significant safety factor to the patient. Both the shortage in supply of crude curare and its variable composition led the search for synthetic curare analogues conferring well defined pharmacodynamic and pharmacokinetic properties. Based on the chemical structure of tubocurarine which has been known since 1935 the efforts concentrated on bisquaternary ammonium compounds. Gallamine was the only synthetic curare analogue to contain three quaternary ammonium groups. This drug had significant undesired vagolytic effects. In 1951 succinylbischoline appeared to be the ideal muscle relaxant, particularly with respect to its fast onset and short duration of action. The disadvantages of its depolarising mechanism of action which were appreciated during the years to follow prevented the concept of depolarising neuromuscular blockade to be pursued further. With other muscle relaxants, including curare itself, histamine release, vagal blockade and ganglionic blockade were undesired effects to be eliminated in future compounds. Improved understanding of structure-activity relationships turned out to be an indispensable tool for future research. This in turn required more elaborate methods in chemical analysis, in electrophysiology of the motor endplate, and in ultrastructural research. As a result, alcuronium and pancuronium became available in the late sixties and early seventies. Both muscle relaxants had a non-depolarising mechanism of action with reduced side effects relative to curare. From now on better techniques for pharmacodynamic and pharmacokinetic research became available resulting in research activity with particular emphasis in this field. Researchers became aware that new muscle relaxants should be designed for larger volumes of distribution and more rapid biodegradation than those currently available. Concurrently, anaesthesia techniques had changed in a way to use intubation and mechanical ventilation as a routine procedure. The risk of intraoperative hypoventilation and hypoxemia was eliminated, yet, due to the lack of adequate monitoring techniques the slow recovery from curare, alcuronium or pancuronium neuromuscular blockade was hardly appreciated.
Curare
People
Muscle relaxants
Curare in history
Neuromuscular blocking muscle relaxants



Refs
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