 The major objective of this study is to examine the effectiveness of memantine on behaviour with a focus on agitation and aggression. The secondary objective is to determine the effect of memantine on nursing burden and prescription medication use. The study would expand clinical experience with memantine and provide information on professional caregiver burden and prescription medication use in this institutionalized, more severely impaired and frailer population. This information could be used to design a randomized placebo controlled confirmatory trial. 