This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
Which drug is not used in Alzheimer's disease 
Select and explain. 
A. Tacrine, B. Gallantamine, C. Donepezil, D. Rivastigmine
A: Tacrine
Answer: A: Tacrine 
Explanation: Refer kDT 6/e p 102,472,473 Because of hepatotoxicity, and requirement of frequent dosing, Tekken is less often used than other agents