Alzheimer's disease (AD), is associated with behavioral disturbances in approximately 50% of AD patients in Beijing. Agitation, and aggression specifically, is considered the most serious noncognitive symptom experienced in patients with dementia. Memantine is a recognized treatment for Alzheimer's disease either alone or in combination with cholinesterase inhibitors. Its efficacy in vascular dementia is also established. Family members continue to play a central role in home care for the demented elderly in China. This proposal is to conduct a study in Beijing, China to investigate the efficacy and safety of Memantine in the treatment of agitation and aggression in AD patients. In addition, this proposal aims to explore the impact of memantine on caregiver burden of AD patients in Chinese culture.

Inclusion Criteria:

1. Written informed consent
2. Clinical diagnosis of Alzheimer's disease.
3. Having at least a minimum aggression score on the Cohen-Mansfield Agitation Inventory (CMAI): a score of ≥ 4 on at least 1 aggressive item, or a score of 3 on at least 2 aggressive items, or a score of 2 on at least 3 aggressive items, or 2 aggressive items occurring at a frequency of 2 and 1 at a frequency of 3.
4. Availability of a responsible family member or carer to ensure treatment compliance and provide information for informant assessments.

Exclusion Criteria:

1. Unavailability of a responsible family member or carer
2. Severe renal impairment.
3. History of seizures
4. Diagnosis of any concomitant life threatening illness.