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Suxamethaonium is used to aid endotracheal intubation of cats.
Suxamethaonium is used to aid endotracheal intubation of cats.
==Non-Depolarising Neuromuscular Blockers==
'''Non-depolarising agents''' are competitive neuromuscular blocking agents. Unlike [[Depolarising Neuromuscular Blockers|depolarising agents]] there are a number of different drugs available for use. They should not be used on concious patients.
===Mechanism of Action===
Non-depolarising agents act by binding to the post synaptic acetylcholine (ACh) receptors, but unlike the [[Neuromuscular Blockers#Depolarising Neuromuscular Blockers|depolarising agents]], do not cause ion channel opening and therefore there is no action potential. However, by binding to the receptors they prevent binding by ACh thereby blocking normal transmission. This means that there is no stimulation before relaxation is seen upon administration. It also only requires binding at one of the two sites on the receptor to have its blocking effect.
===Pharmacological Considerations===
Non-depolarising agents can be administered intravenously. Onset and duration of action varies between 2-5 minutes depening on the drug used (see below). Electrolyte imbalances can potentiate the action of these agents.
==Drugs in this Class==
===Contraindications and Side Effects===
*Response to these drugs may be altered by underlying neurological conditions that are present in patients e.g. myasthenia gravis patients have a reduced number of ACh receptors and so are more sensitive where as patients with denervating diseases are less sensitive as there are increased numbers of ACh receptors.
*Patients with hepatic or renal disease may have prolonged recovery time after the administration of vecuronium or pancuronium due to hepatic metabolism and renal excretion impairment.
*Increases in heart rate and blood pressure may be seen.
*Atracurium has been associated with histamine release reactions - This is reduced with the use of cis-atracurium.
===Clinical Uses===
Non-depolarising agents can be used during surgery to improve muscle relaxation and also allow for mechanical ventilation.
===Drugs in this Class===
'''Atracurium'''
:Onset of action is approximately 3-5 minutes.
:Duration of action is approximately 20-35 minutes.
:Metabolised by non-specific esterases, and so independent of hepatic or renal function.
:Potential histamine release reactions.
'''Cis-atracurium'''
:Isomer of atracurium - More potent.
:Not associated with histamine release.
'''Vecuronium'''
:Onset of action is approximately 2-3 minutes.
:Duration of action is approximately 30-45 minutes.
:Minor hepatic metabolism but depends on biliary excretion to terminate its effect.
'''Pancuronium'''
:Onset of action is approximately 2 minutes.
:Duration of action is approximately 25 minutes.
:Ocassionally see tachycardia and hypertension.
[[Category:Anaesthetic Drugs]]
[[Category:Anaesthetic Drugs]]