Action of Some Specific Muscle Relaxants

The probable and proven mode of action of eertain selected musele relaxants discussed in this chapter shall be dealt with in the section that follows. 

It is foimd to be 2 to 4 times more potent than tubocurarine (+ TB). In man, it is eliminated ehiefly by renal and biliary exeretions the half-life is about 3.5 hour. It is observed that it can safely pass aeross the plaeental barrier. 

Its mechanism of action normally is assumed to be almost similar to that of d-tubocurarine (+TB), but the dose-response curve is rather steeper in nature thereby suggesting a possible difference. The cardinal differences with respect to + TB are, namely (a) it fails to block the autonomic ganglia (side-effect) and b) it rarely releases histamine , hence it fails to cause either bronchospasm or hypotension. It is found to have little effect on the circulatory system. 

Interestingly, anticholinesterases, ACH and ion antagonize competitively pancuronium bromide effectively however, its activity is virtually enhanced by general anaesthetics, for instance halothane, ether, enflurane etc. (see Chapter 4). Therefore, the latter substantial potentiation in pharmacological activity is particularly useful to the anaesthetist due to the faet that it is administered invariably as an adjunct to the anaesthetic procedure in order to cause simultaneous relaxation of the skeletal muscle. 

It usually has an extemely transient duration of action by virtue of the fact that it imdeigoes rapid hydrolysis by the help of serum butyryl (pseudo) cholinesterases. However, a prolonged muscular 

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MODE OF ACTION OF SOME SPECIFIC MUSCLE RELAXANTS ... 

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