Neostigmine is not able to cross blood brain barrier because of its: (A) Primary structure, (B) Secondary structure, (C) Teritiary structure, (D) Quaternary structure
Answer is D. Quaternary ammonium compounds are water soluble and thus cannot cross blood brain barrier neostigmine is a quaternary derivatives where as physostigmine is a teritiary amine Ref-KDT 6/e p101