<prompt> Which of the following drug do not cross the blood-brain barrier?Diacetyl monoximeObidoximinePhysostigmineNeostigmine  <response>: Neostigmine being a quaternary ammonium compound and highly polar cannot cross BBB.Pralidoxime which is used in OP poisoning also can;t cross the BBB.Ref: Katzung 11th ed.Pg 121 