To date, there are many drugs had been approved and licensed for curing this disease, such as rivastimine, donepezil and galanthamine. At a certain extent, they are generally considered as cholinesterase inhibitors. Although these drugs share the same therapeutic class, they differ in their pharmacology and pharmacokinetics and possess different degree side effects. Moreover, they just cure mild or moderate degree of AD at the early stage, still no cure for severe type of AD