Prazosin Treatment for Disruptive Agitation in Alzheimer's Disease

This is a 24 week study with 14 visits to the research clinic. Approximately 6 of these visits may be done by phone. Additional phone checks are scheduled at the beginning of each 12 week part of the study. Participants will have a 50:50 chance of being on prazosin or placebo in the first 12 weeks of the study. For the second 12 weeks, all participants will take prazosin. Study visits include a physical and neurological exam; memory testing; interviews with the caregiver about behaviors; and vital signs.