NEUROMUSCULAR-TRANSMISSION AND ITS PHARMACOLOGICAL BLOCKADE .2. PHARMACOLOGY OF NEUROMUSCULAR BLOCKING-AGENTS

Clinically, neuromuscular blockade is induced with either depolarizing or non-depolarizing relaxants. Suxamethonium is the only depolarizing relaxant still in use. It is hydrolysed in Is the plasma by pseudo-ch olinesterase (plasma cholinesterase). In some patients and in particul ar diseases the plasma cholinesterase activity is low and hence the ef fect of suxamethonium prolonged. Suxamethonium is characterized by sid e-effects such as myalgia, fasciculations and in intraocular, intracra nial and intragastric pressure; More serious adverse reactions are mas seter muscle spasm and potassium release, in patients with some neurom uscular diseases and increase in extrajunctional acetylcholine recepto rs. As non-depolarizing muscle relaxants benzylisoquinolines and stero idal compounds are mainly used. Each relaxant has its own pharmacologi cal characteristics. The effect of most relaxants depends on liver and renal function because the pharmacokinetic behaviour is strongly depe ndent on these organs. Also, acid-base balance disturbances, change in temperature, and neurological diseases have an effect on the profile of the relaxants. A number of drugs (anaesthetics, antibiotics, antiep ileptics, etc.) have an effect on neuromuscular transmission, and thus interact with the relaxants. Some non-depolarizing relaxants cause hi stamine release and cardiovascular effects.