Correct Answer - B
Local anaesthetics blocks nerve conduction by decreasing the entry of sodium ions during
upstroke of action potential.
Finally it blocks depolarization to reach threshold potential and conduction block occurs.
Small fibers are more sensitive to local anaesthetics than large fibers and non myelinated
fibers are blocked easily than myelinated fibers.
Ref: Essentials of Medical Pharmacology by K D Tripathi, 5th Edition, Pages 321-3

Correct Answer - A
Ans. is 'a' i.e., Mivacurium
Suxamethonium (succinylcholine) is the shortest acting skeletal
muscle relaxant. o Mivacurium is the shortest acting nondepolarizing
skeletal muscle relaxant.

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Correct Answer - A
Ans. is 'a' i.e., Succinylcholine
Succinylcholine
SCh is a depolarising skeletal muscle relaxant.
It causes sustained partial depolarization of muscle end plate —>
intially produce twitching and fasciculation followed by flaccid
paralysis.
It is the shortest and fastest acting skeletal muscle relaxant.
It is the only muscle relaxant which stimulate autonomic ganglia and
vagus.
SCh is the most commonly used muscle relaxant for passing
endotracheal tube (mivacurium and rocuronium are alternatives).
SCh is rapidly hydrolysed by plasma cholinesterase, some patients
have genetically determined abnormality or deficiency of
pseudocholinesterase, in them, SCh causes phase II block.
It can cause muscle fasiculations and soreness, change in BP and
HR, arrythmia, histamine release and IC efflux from muscles.
Dangerous hyperkalemia can occur in patients with burn, crush
injury, muscular dystrophy, GB. Syndrome, paraplegia or
hemiplagia, mysthenia gravis and rhabdomyolysis contraindicated in
such patients. o It can accentuate malignant hyperthermia caused
by halothane.
SCh causes increase in all pressures —> inraocular, intracranial,
BP, and intrabdominal —> contraindicated in glaucoma, head injury.