Neuromuscular drugs

The neuromuscular drug atracurium (Chapter 11) is a good example of this. 

Short-acting ester-containing neuromuscular drugs, such as succinylcholine (Anec-tine, 2) (Fig. 15.3) and mivacurium chloride (Mivacron) (61) designed to undergo hydrolysis by human plasma cholinesterase, also exploit similar principles, to ensure fast and spontaneous recovery upon cessation of administration. Hence, their durations of action are only 6-8 and 12-18 min, respectively,and the corresponding elimination routes remain functional even in renal failure. 

Brueckner J, Thomas KC, Bikhazi GB, Foldes FF. Neuromuscular drug interacticms of clinical impK>rtance. AnesthAnalg (1980) 59,533-4. 

R = / -C H ), in low doses, exhibits the former behavior and is used primarily as an extradural agent in obstetrics. The lowest effective extradural concentration of etidocaine (21, X = CH, R = R = 2H, R = / -C H ), however, shows both adequate sensory and profound motor blockade so that it is useful in surgical situations where maximum neuromuscular blockade is necessary. In an isolated nerve preparation, bupivacaine blocks unmyelinated C fibers which are mainly responsible for pain perception at a much greater extent than the myelinated A fibers which carry motor impulses. It is postulated that absorption of bupivacaine by the vasculature at the site of injection, combined with the slow diffusion of this agent, results in an insufficient amount of the drug penetrating the large A fibers to cause motor conduction blockade. Clinically, motor block can be observed in some procedures. 

When kaolin or aluminum is administered widi die lincosamides, die absorption of the lincosamide is decreased. When the lincosamides are administered with the neuromuscular blocking drag (drag diat are used as adjuncts to anesthetic drag diat cause paralysis of the respiratory system) die action of die neuromuscular blocking drug is enhanced, possibly leading to severe and profound respiratory depression. 

UNIT IV Drugs That Affect the Neuromuscular System... 

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