Efficacy and Safety of Memantine in Moderate to Severe Alzheimer's Disease

Inclusion Criteria: Outpatients who: * had a primary diagnosis of probable Alzheimer's Disease (AD) according to National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINDS-ADRDA) criteria, and with Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revised (DSM IV TR) criteria for dementia of the Alzheimer's type * had moderate to severe dementia, defined as a Mini Mental State Examination (MMSE) total score \>=5 and \<=15 at screening. Before substantial protocol amendment SA04 (dated 7 October 2004) was implemented, the MMSE total score range at screening was \>=8 and \<=18. Substantial protocol amendment SA07 (dated 4 September 2009) allowed patients who had previously had an MMSE score of 16 or 17 to be re-screened \>6 months after their initial screening and, if there was documented evidence of cognitive decline, to be enrolled in the study * had a Neuropsychiatric Inventory (NPI) total score \>=13 and an NPI agitation/aggression subitem score \>=1 at screening and baseline * did not have vascular dementia or a modified Hachinski Ischaemia Scale score \>4 at screening Exclusion Criteria: * Evidence of clinically significant active disease, evidence of other neurological disorders, and previous treatment with memantine