This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parasympathetic System & Glaucoma, Subject name: Pharmacology
[{'content': 'Which of the following is longest acting cholinesterase inhibitor used for myasthenia gravis? \nSelect and explain. \nA. Pyridostigmine, B. Edrophonium, C. Neostigmine, D. Physostigmine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Both neostigmine and pyridostigmine are used in myasthenia gravis. Pyridostigmine is longer acting than neostigmine. These drugs act by inhibiting acetylcholinesterase. Edrophonium is very sho acting anti-cholinesterase and is preferred drug for diagnosis of myasthenia gravis. Physostigmine is a lipid soluble anticholinesterase used in glaucoma and atropine poisoning.', 'role': 'assistant'}]