This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Which drug is not used in Alzhermer's disease 
Select and explain. 
A. Tacrine, B. Galantamine, C. Donepezil, D. Rivastigmine
A: Tacrine
Answer: A: Tacrine 
Explanation: Ans. is 'a' i.e., Tacrine o Recently 4 cholinergic activators (cerebroselective anticholinesterase drugs) are being approved by UK & USA for use in AD Tacrine, Rivastigmine, Donepezil, Galantamine. o Because of hepatotoxicity, and requirement of frequent obsing, tacrine is less often used than other agents.