Safety and Efficacy of Donepezil in Mild to Moderate Alzheimer's Disease

Inclusion Criteria: 1. Patients between 50 and 85 years of age. 2. Patients newly diagnosed as probable AD based on Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR) criteria and National Institute of Neurologic and Communicative Disorders and Stroke-AD and Related Disorders Association (NINCDS-ADRDA) criteria; Mild to moderate AD with Mini-Mental State Examination (MMSE) 10-24, modified Hachinski ischaemic scale (MHIS)≤4, Activity of daily life scale (ADL)≥23, and Hamilton Depression Scale (HAMD) \<7. 3. MRI image supports the diagnosis of AD (medial temporal lobe atrophy, Fazekas scale of white matter lesions≤2 within 6 months prior to the screening). 4. 5mg daily of Donepezil for at least four weeks before the screening. 5. Patient with exclusive caregiver. 6. Patient should be ambulatory or ambulatory aided by a walker or cane. 7. With good eyesight and hearing, can cooperate with the examination and treatment. Exclusion Criteria: 1. Patients with vascular dementia, other types of dementia or with other psychiatric or neurological disorders (e.g. delirium, depression, Parkinson's disease, etc.). 2. Patients with type I diabetes, obstructive lung disease or asthma, vitamin B12 or folic acid deficiency, thyroid dysfunction, severe liver or kidney dysfunction, severe cardiac insufficiency (congestive heart failure, myocardial infarction, sick sinus syndrome, II-III degree atrioventricular block or heart rate\<50 beats/minute \[bpm\]). 3. Epilepsy or head trauma resulting in unconsciousness that occurred in the two years prior to the screening. 4. Patients with hematologic diseases (such as anemia, granulocytes, leukemia, etc.), tumor, neoplasms within 2 years prior to the screening. 5. Patients with a history of alcohol dependence and drug abuse. 6. Patients with known hypersensitivity to medicines or foods; 7. Patients taking anticholinergic agents or antihistaminic agents; 8. Patients who had been hospitalized continuously for more than 3 months before the screening.