Inclusion Criteria:
A patient is eligible for the study if all of the following apply:
1. With either gender aged at least 40 years old
2. With a diagnosis of one of the following disease i. Vascular dementia according to the NINDS-AIREN International Workshop criteria or ii. Alzheimer's disease according to the NIAAA criteria iii. "Mixed" dementia (possible Alzheimer's disease with cerebrovascular disease) according to the NIAAA criteria
Note:
1. NINDS-AIREN: National Institute of Neurological Disorders and Stroke and Association Internationale pour la Recherche et l'Enseignement en Neurosciences
2. NIAAA: National Institute on Aging-Alzheimer's Association
3. With mild-to-moderate dementia (score of the Mini-Mental State Examination (MMSE) defined as between 10 to 24)
4. Able to read, write, communicate, and understand cognitive testing instructions
5. Having a responsible caregiver who spends adequate time daily with the patient; the caregiver will accompany the patient to all clinic visits during the study and supervise all study dosing requirements and concomitant medications
6. Signed, by patients and the responsible caregiver, the written informed consent form
Exclusion Criteria:
1. With large-artery stroke (thrombotic stroke)
2. With radiological evidence of other brain disorders (subdural hematoma, post-traumatic / post-surgery)
3. With dementia caused by other brain diseases except Alzheimer's disease and vascular dementia (e.g. Parkinson's disease, demyelinated disease of the central nervous system, tumor, hydrocephalus, head injury, central nervous system infection including syphilis, acquired immune deficiency syndrome, etc.)
4. With clinical evidence of pulmonary, hepatic, gastrointestinal, metabolic, endocrine or other life threatening diseases judged by investigators not suitable to enter the study
5. With clinically unstable hypertension, diabetes mellitus, and cardiac disease for the last 3 months
6. With history of stroke and hospitalized for stroke in the previous 3 months
7. With history of alcohol or drug abuse
8. With one of the following abnormal laboratory parameters: hemoglobin \< 10 mg/dL or platelet \< 100\*109/L; creatinine or total bilirubin more than 1.5 times the upper limit value; alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphates (ALP), or γ-glutamyl transferase (γ-GT) more than 2 times the upper limit of normal
9. With depression, not well-controlled with medications.
10. With any uncontrolled illness judged by the investigator that entering the trial may be detrimental to the patient
11. With known or suspected hypersensitivity to any ingredients of study product and vehicle
12. Pregnant or lactating or premenopausal with childbearing potential but not taking reliable contraceptive method(s) during the study period
13. Enrollment in any investigational drug trial within 4 weeks before entering this study
