The purpose of this study is to see if a medication called prazosin is useful in the treatment of agitation and aggression in persons with Alzheimer's disease (AD) and other types of dementia in late life.

Although the occurrence of disruptive agitation behaviors likely are influenced by environmental/ interpersonal factors, it is also likely that behaviorally relevant neurobiologic abnormalities lower the threshold for the expression of such behavior in Alzheimer's disease. Because of the success prazosin has had in the treatment of Posttraumatic Stress Disorder, it is thought that it could be used similarly with disruptive agitation. Originally designed to evaluate Alzheimer's disease patients in nursing homes, the study now includes outpatients. It is a 9-week placebo-controlled trial.

Inclusion Criteria:

• No age limit
• probable/possible Alzheimer's disease diagnosis
• disruptive agitated behaviors (e.g., irritability, aggression, uncooperativeness, pacing)
• no hypotension
• no concurrent use of alpha-1-blockers
• no delirium, schizophrenia, mania, psychotic symptoms.

Exclusion Criteria:

• Cardiovascular: unstable angina, recent myocardial infarction, second or third degree atrioventricular (AV) block, preexisting hypotension (systolic blood pressure less than 110) or orthostatic hypotension
• Other medical exclusions: chronic renal or hepatic failure, or any unstable medical condition
• Exclusionary medications: current treatment with prazosin, other alpha-1-blockers
• Current enrollment in a separate investigational drug trial
• Psychoactive medications: subjects may be psychoactive medication-free or be partial responders (by subjective assessment of referring health care professional) to one psychoactive medication from any of the following classes: antipsychotics, anticonvulsants, mood stabilizers, antidepressants, benzodiazepines, or buspirone. Partial response is defined as some improvement in agitated behavior but persistence of agitated behaviors severe enough to cause patient distress and/or difficulty with caregiving. Although not formally rated, this improvement is equivalent to a Clinical Global Impression of Change (CGIC) rating of no more than minimal improvement (improvement is noticed by not enough to improve patient function or caregiver's practical management of the patient).
• Psychiatric/behavioral: lifetime schizophrenia; current delirium, mania, depression, or uncontrolled persistent distressing psychotic symptoms (hallucinations, delusions), substance abuse, panic disorder, or any behavior which poses an immediate danger to patient or others or which results in the patient being too uncooperative to meet the requirements of study participation.

Adverse event data were collected from informed consent up until volunteers reached the end of their participation per protocol. Monitoring period was 10-12 weeks (2-4 weeks to start and titrate study drug, plus the 8 week follow-up period).

Adverse effects were collected at each study visit. Study staff inquired about specific symptoms known to be potential side effects of prazosin using a preexisting checklist. Participants and their study companions were also asked about any new changes in health or medications.