Muscle relaxants are neuromuscular blockers that cause relaxation of the skeletal muscles. They represent nitrogen compounds with an affinity for N-cholinoreceptors. They are used in anesthesiology to induce a prolonged paralysis - a prerequisite for long lasting interventions. The nature of these drugs, improper dosing and clinical indications carry their appropriate health risks.
Some muscle relaxants are an analogue of acetylcholine and thus easily bind to ACh receptors but, unlike them, they are not metabolized by the enzyme acetylcholinesterase. The occurring prolonged depolarization leads to muscle relaxation – hence the name depolarizing muscle relaxants. That includes suxamethonium chloride (succinylcholine), brand name Lysthenon. Application of this medicine is not recommended for patients with pulmonary edema, severe hepatic dysfunction, history of malignant hyperthermia, hyperkalemia and others. It may cause allergic reactions such as bronchospasm. Combination with other drugs suppresses or potentiates its action. In children and adolescents Lysthenon can cause irreversible cardiac arrest so its use is limited to cases in need of an immediate endotracheal intubation.
The majority of non-depolarizing muscle relaxants are not metabolized by the ACh-esterase. They bind irreversibly to the cholinergic receptor and produce stoichiometric changes in it. Their metabolusm is not organ-dependent – the so-called Hofmann elimination. Intermediate metabolites may lead to side effects - such as CNS hyperexcitability and seizures (Laudanozin toxicity).
Cardiovascular events and allergic reactions have also been observed. Non-depolarizing muscle relaxants include Atracurium (Tracrium), Cisatracurium, Pipecuronium (Arduan), Rocuronium (Esmeron), Pancuronium (Pavulon), Doxacurium, etc.
Usually in clinical practice a particular drug becomes universal and is used on many patients despite the existence of minimal clinical risks. Better understanding of muscle relaxants, their properties and side effects promises an optimal and safe use.
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