Neuromuscular blocking activities of some steroidal mono and bis-quaternary ammonium compounds with special reference to NN'-dimethylconessine

Development of ultra short-acting muscle relaxant agents: History, research strategies, and challenges

Author has reviewed the literature and his own work related to the chemistry, pharmacology, and clinical aspects of new muscle relaxants. Emphasis has been placed on the basic science concepts and technologies (e.g. structure-activity relationships, nicotinic receptor pharmacology, and investigation of side effects) behind the development of rapidly and short acting nondepolarizing muscle relaxants.

Prelude to pancuronium and vecuronium

The discovery of the neuromuscular blocking activity of malouetine isolated from Malouetia bequaertiana Woodson by Quevauviller and Lainé in 1960 stimulated interest in aminosteroids as potential neuromuscular blockers. Alauddin (a pharmacist) and Martin-Smith (a medicinal chemist) began research in this area, which was then taken up by pharmaceutical companies. Pure pancuronium was synthesised in 1964 by Savage and his co-workers, directed by Hewett. Pharmacologists headed by Buckett discovered that pancuronium was far more potent than d-tubocurarine and had minimal side-effects. Buckett quickly recognised the value of pancuronium, and his persistence resulted in successful clinical trials, followed by the commercial launch of pancuronium in 1968. Vecuronium was synthesised, tested and the studies published by Buckett, Hewett and Savage in 1973, but this was before anaesthetists called for a 'clean muscle relaxant' and, furthermore, it was unstable in aqueous solution. Hence, it was only promoted for clinical trials six years later.

Factors limiting the rate of termination of the neuromuscular blocking action of fazadinium dibromide

1 Reasons for the termination of the neuromuscular blocking action of fazadinium dibromide have been investigated. 2 In the anaesthetized cat, maximum neuromuscular block of tibialis anterior muscle twitches following rapid intravenous injection of fazadinium was obtained as the injection bolus passed through the muscle, indicating the fazadinium very readily crosses capillary membranes. 3. The half-life of plasma clearance of fazadinium was about 1 min in both cat and man, despite a 10 fold difference in duration of action in these species. Plasma samples were bioassayed for neuromuscular blocking activity on an isolated, superfused phrenic nerve-diaphragm preparation of the rat. 4 In the anaesthetized cat, occlusion of the renal or hepatic circulations did not prolong the neuromuscular blocking action of single doses of fazadinium. Repeated doses accumulated slowly when the hepatic circulation was occluded but not when the renal circulation was occluded. 5 Fazadinium is eliminated from the body by both the liver and kidneys but the rates of these processes are insufficient to account for the initial rapid plasma clearance. 6 The rate-limiting step for the termination of the neuromuscular blocking action of fazadinium is most likely to be the rate of drug-receptor dissociation

The neuromuscular blocking activity of some monoquaternary androstane derivatives

The neuromuscular blocking activity of some 3- or 17-monoquaternary derivatives of 3β,17β-dipyrrolidin-1′-yl-5α-androstane has been examined in the cat. 3-Monoquaternary salts were, in general, more potent than the 17-monoquaternary salts. It was concluded that the presence of a quaternary group in position 3 is an important determinant of potency in this series of androstane derivatives.