Muscle relaxants, adverse drug reaction

Watkins J. Heuristic decision-making in diagnosis and management of adverse drug reactions in anaesthesia and surgery the case of muscle relaxants. Theor Surg 1989 4 212. 

Drowsiness is the most common reaction seen with the use of skeletal muscle relaxants. Additional adverse reactions are given in die Summary Drug Table Drugp Used to Treat Musculoskeletal Disorders. Some of the adverse reactions tiiat may be seen with the administration of diazepam include drowsiness, sedation, sleepiness, letiiargy, constipation or diarrhea, bradycardia or tachycardia, and rash. 

Neurotoxicity is a rare adverse reaction that can be recognized by perioral paresthesia, numbness, weakness, ataxia, and blurred vision. These drugs may precipitate respiratory arrest both in patients given muscle relaxants during anesthesia and in persons with myasthenia gravis. 

Cyclobenzaprine is structurally closely related to the tricyclic antidepressants (see later) and therefore shares many of their adverse reactions. These include drowsiness (CNS effects), dry mouth (anticholinergic effects), and dizziness. The potential for serious interactions with MAO inhibitors also exists. Nevertheless, the drug s centrally acting skeletal muscle relaxation is useful for short-term treatment of local muscle spasms. 

Smith (1957) described cases of reactions to suxamethonium and other muscle relaxants, which occurred on the first exposure to these drugs, and therefore, could only be explained by direct histamine release. That many drugs or other chemicals can act as histamine releasers has been known for a long time (Paton 1957). The review by Paton (1957) included neuromuscular blocking drugs. However, the most relevant question which has not been answered so far is why should some patients react so adversely to those agents in the absence of evidence of allergy ... 

Assem ESK (1977) Examples of the correlation between the structure of certain groups of drugs and adverse effects mediated by immune and non-immune mechanisms (with particular reference to muscle relaxants and steroid anaesthetics). In Bundgaard H, Juul P, Kofod H (eds) Drug design and adverse reactions. Munksgaard, Copenhagen, pp 209-226... 

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