Long-term safety and efficacy of donepezil in patients with severe Alzheimer's disease: results from a 52-week, open-label, multicenter, extension study in Japan.

Background/Aims: A 6-month, randomized, double-blind, placebo-controlled study was extended to evaluate long-term safety and efficacy of donepezil in community-dwelling Japanese patients with severe Alzheimer’s disease (AD). Methods: 189 patients were enrolled from the double-blind study into a 52-week, open-label extension study. After a 2- to 8-week washout, donepezil was escalated within 6 weeks to 10 mg/day. Main outcomes were Severe Impairment Battery (SIB), Alzheimer’s Disease Cooperative Study-Activities of Daily Living scale for severe AD (ADCS-ADL-sev) and Behavioral Pathology in Alzheimer’s Disease Rating Scale (BEHAVE-AD). Safety parameters were monitored throughout. Results: Overall, mean change from extension study baseline in SIB scores improved until week 24; however, scores were influenced by prior treatment during the double-blind study and by length of washout. Patients treated with donepezil retained some treatment benefits after a washout of 2–4 weeks but lost all treatment benefits after a washout of 4–8 weeks. There was no change in ADCS-ADL-sev or BEHAVE-AD scores. Adverse events were consistent with the known donepezil safety profile. Conclusion: Donepezil is effective and safe for symptomatic treatment of severe AD for at least 1 year. Patients who receive donepezil 10 mg daily with little or no interruption achieve the best long-term outcome.