<prompt> Neostigmine -It is a quaarnary amounium compoundMetabolised in liverIt can cross the blood brain harrierProminent effect on smooth muscles  <response>: Ans. is a i.e., It is a quaarnary amounium compound Teiary amine Vs quaenary ammonium compound o Neostigmine is a quaenary ammonium compound. o Quaenary ammonium compounds are lipid insoluble and diffuse poorly across the membrane : - Li Oral absorption --- Poor CNS penetration -- poor No CNS action Applied to eye No penetration of cornea. More marked effect on skeletal muscles, ganglia, but muscarinic effects are less prominant. o In contrast, physostigmine is a teiary amine derivated. o Teiary amine compounds are lipid soluble and diffuse easily across the membrane :- Oral absorption Good CNS penetration -- Good Produce CNS actions. Applied to eye -- Penetrate cornea. More marked muscarinic and CNS effect. 