Neostigmine is not able to cross blood brain barrier because of its:
Ans. (D) Quarternary structure(Ref: KDT 8th/e p116)Quarternary ammonium compounds are water soluble and thus cannot cross blood brain barrier. Neostigmine is a quarternary derivative whereas physostigmine is a tertiary amine.
Primary structure
Secondary structrure
Tertiary structure
Quarternary structure
A.N.S.