Skeletal muscle relaxants neuromuscular blocking drugs

Drugs discussed in this chapter are used to decrease muscle excitability and contraction via an effect at the spinal cord level, at the neuromuscular junction, or within the muscle cell itself. Some texts also classify neuromuscular junction blockers such as curare and succinylcholine as skeletal muscle relaxants. However, these drugs are more appropriately classified as skeletal muscle paralytics because they eliminate muscle contraction by blocking transmission at the myoneural synapse. This type of skeletal muscle paralysis is used primarily during general anesthesia using neuromuscular blockers as an adjunct in surgery was discussed in Chapter 11. Skeletal muscle relaxants do not typically prevent muscle contraction they only attempt to normalize muscle excitability to decrease pain and improve motor function. 

Before the introduction of neuromuscular blocking drugs, profound skeletal muscle relaxation for intracavitary operations could be achieved only by producing levels of volatile (inhaled) anesthesia deep enough to produce profound depressant effects on the cardiovascular and respiratory systems. The adjunctive use of neuromuscular blocking drugs makes it possible to achieve adequate muscle relaxation for all types of surgical procedures without the cardiorespiratory depressant effects produced by deep anesthesia. 

Leuwer M, Motsch P 1996 Neuromuscular blocking agents and skeletal muscle relaxants. In Dukes M N G (ed), Meyler s side-effects of drugs. Elsevier, Amsterdam, pp. 298-346... 

Muscle Nitrous oxide does not relax skeletal muscle or enhance the effects of neuromuscular blocking drugs. Unlike the halogenated anesthetics, N O does not trigger malignant hyperthermia. 

C. Neuromuscular Blocking Drugs Neuromuscular blocking drugs are important for producing complete skeletal muscle relaxation in surgery new ones are frequently introduced. They are discussed in greater detail in Chapter 27. 

In general, skeletal muscle relaxants may be classified as (a) Neuromuscular Blocking Drugs and (b) Centrally Acting Muscle Relaxants. 

Muscle Isoflurane produces some relaxation of skeletal muscle via its central effects. It also enhances the effects of depolarizing and nondepolarizing muscle relaxants. Isoflurane is more potent than halothane in its potentiation of neuromuscular blocking agents. The drug relaxes uterine smooth muscle and is not recommended for analgesia or anesthesia for labor and vaginal delivery. 

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