Prazosin Treatment for Disruptive Agitation in Alzheimer's Disease

Inclusion Criteria: * No age limit * Probable or Possible Alzheimer's Disease * Disruptive agitated behaviors at least twice a week (overly anxious or excited, making offensive comments.....) * Stable medications for 2 weeks * Must have a caregiver who spends 10 hours per week caring for the participant and agrees to participate in all evaluation sessions Exclusion Criteria: * Cardiovascular: unstable angina, recent myocardial infarction, preexisting hypotension (systolic BP less than 110) or orthostatic hypotension (≥20 mmHg drop in systolic BP following 2 minutes of standing posture) * Any unstable medical condition * Exclusionary medications: current treatment with prazosin, other alpha-1 blockers (trazodone, sildenafil, vardenafil or tadalafil) * 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 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.