<prompt> Shoest acting anticholinesterase is -EdrophoniumPyridostigmineGlycopyrrolateNeostigmine  <response>: Ans. is a i.e., Edrophonium o Edrophonium is the shoest acting anti-ChE. o Why is it so, lets see : o When carbamates other than edrophonium and organophophates react with cholinesterase, they form covalent bond at esteratic site, which is considerably resistant to hydrolysis. o In contrast, edrophonium binds electrostatically and by hydrogen bonds at anionic site not at esteratic site of cholinesterase. The enzyme inhibitor complex does not involve a covalent bond and is correspondingly sho lived 2-10 minutes. o So edrophonium is also called as noncovalent inhibitor. 