Question

Compare and contrast the mechanisms of action of nondepolarizing and depolarizing neuromuscular blocking agents and state how these actions influence the use of one class rather than the other in specified clinical situations.

Answer 1

	NDP Neuromuscular Blocking Agent	DP Neuromuscular Blocking Agent
	D tubocurarine,pancuronium etc are example	Succinylcholine,decamethonium are example
site of action	End plate of skeletal muscle fibre	End plate of skeletal muscle fibre
	They have affinity for nicotinic cholinergic receptor but no intrinsic activity.They are competitive blocker.They have a bulky thick structure. ACH released from motor nerve ending can not generate end plate potential.Fall of EPP leads to non generation of MAP or muscle action potential following nerve impulse.Here the NDP blocks the sodium channel for neuromuscular block.	Affinity is there for nicotinic cholinergic receotor but also intrinsic action.this action is absent in NDP agents Depolarize muscle end plate by opening sodium channel which initially produce twitching and fasciculation.in a multiply innervated muscle stimulation is prolonged. So contraction is long lasting there..These drugs are not hydrolyzed by AChE. so stays in the receptor end for long. As a result prolonged partial depolarization around muscle end plate occur causing dropping of transmembrane potential below-50mV. resulting in Na channel inactivation occur resulting in flaccid paralysis.

Use....IV of NDP rapid production of weakness of the muscle followed by flaccid paralysis.Fingers extraocular muscles are affected first then large limbs and lastly diaphragm,Recovery occurs in the reverse order respiration resumes first by diaphragmatic contraction.

IV DP A very rapid flaccid paralysis occur in anesthesia