Two common side effects of Aricept (Donepezil) are insomnia and stomach pain. I worked for 6 years as an RN Cognitive Specialist (Psych Nurse) for a large home health company, and I was often called out to Memory Care Units to assist Alzheimer’s clients that had suddenly developed psychosis (audio and/or visual hallucinations, typically accompanied by increased agitation). In many cases the psychosis was caused by sleep deprivation, and when we stopped Aricept things would often improve rapidly. I was getting dozens of people per year off of Aricept and never saw a negative outcome. Many doctors advise that it should only be used in the early stages of the disease and immediately discontinued if there is no improvement. I strongly agree with this, as the side effects, especially sleep disturbance, are a real problem.