Neostigmine does not able to cross blood brain barrier because of its: (A) Primary structure, (B) Secondary structure, (C) Teiary structure, (D) Quaternary structure
Answer is D. Refer kDT 6/e p 101 Quaternary ammonium compounds are water soluble and thus cannot cross blood brain barrier. New Stickman is a quaernary derivative whereas physostigmine is a teiary amine