ABSTRACT
This chapter explores the structure-activity relationships of quaternary amino- and azasteroids which possess high neuromuscular blocking activity and some of them are clinically useful agents. The first use of neuromuscular blocking agents in anesthesiological practice in 1942 revolutionized the practice of anesthesia and started the modern era of surgery. The drug to be introduced as an adjuvant to anesthesia was a crude but standardized preparation called "Intocostrin" containing tubocurarine. Nondepolarizing acetylcholine antagonists are also often described as competitive neuromuscular blocking drugs. These drugs combine with the same receptors as the endogenous agonist, acetylcholine, and inhibit the receptor-agonist interaction. All neuromuscular blocking agents in clinical use act either by depolarizing the motor endplate or by competing with the chemical transmitter acetylcholine at the neuromuscular junction. The conessine-type quaternary compounds are short-acting neuromuscular blocking agents of nondepolarizing type with rapid onset of action and low cumulation propensity.
