<prompt> Longest acting muscle relaxant is-AtracuriumVecuroniumDoxacuriumRocuronium  <response>: Ans. is c i.e., Doxacurium o Amongst the given options doxacurium is longest acting Duration of action 90-120 minutes,o Rocuronium duration of action 30-60 minutes, Atracurium duration of action 30-60 minutes and vecuronium duration of action 60-90 minutes have shorter duration of action than doxacurium.Properties of NM Blockerso Longest acting Neuromuscular blocker - Pancuronium duration of action 120-180 minutes. Goodman Gilman llthe p. 222 Note: In some books pipecuronium or Doxacurium have given as the longer activity,o Shortest and fastest acting neuromuscular blocker - Succinylcholine suxamethonium - duration of action 5-8 minutes.o Shortest acting competitive nondepolarizing neuromuscular blocker - Mivacurium duration of action 12-18 minutes.o Fastest acting nondepolarizing blocker - Rocuronium can be used for endotracheal intubation as an alternative to Sch.o Non-depolarizing neuro-muscular blockers can cause ganglion block, vagal block and Histamine release different agents has different propensity.o Histamine release is caused by - D-TC maximum tendency, succinylcholine, mivacurium, doxacurium, atracurium, tubocurarine - can cause bronchoconstriction.o Virtually no histamine release - Pancuroniumo Vagal block is caused by - Pancuronium, recuronium, Gallamine.o Maximal vagal block and tachycardia is caused by - Pancuronium Previously it was gallamine, but it is not used now.o Vagal stimulation is caused by - succinylcholine can cause bradycardia.o Ganglion block is caused by -d-Tc, Meiocurine, Alcuronium.o Maximum ganglion blockade is caused by - d-TC.o Ganglion stimulation is caused by - Succinylcholine.o Most commonly used muscle relaxant for routine surgery - vecuronium.o Most potent skeletal muscle relaxant - Doxacurium.o Least potent skeletal muscle relaxant - Succinylcholine Gallamine was east potent but it is not used now.o Least potent nondepolarising muscle relaxant - Rocuronium.o MR of choice for - intubation - Sch 1st choice, Rapacuroium 2nd choice, Rocuronium 3rd choice,o Mivacurium is the only non-depolarizing blocker that is metabolized by plasma cholinesterase.o Gallamine was the most nephrotoxic NM blocker - was contraindicated in renal failure. Due to its nephrotoxic and tetratogenic potential it has been withdrawn,o Recuronium produces pain on injection.o Succinylcholine is the muscle relaxant of choice for rapid endotracheal intubation. Rapacuronium and rocuronium are alternates. 