<prompt> Which of the following provides the best explanation for neostigmine being preferred over physostigmine for treating myasthenia gravis?It is better absorbed orallyIt has longer duration of actionIt has additional direct agonistic action on nicotinic receptors at the muscle end plateIt penetrates blood brain barrier  <response>: Neostigmine is a quaternary ammonium derivative and is water soluble. Its absorption from GIT and penetration in the brain and cornea is much less than physostigmine. It produces additional action on NM receptors. 