Efficacy and Safety of Donepezil 23 mg versus Donepezil 10 mg for Moderate-to-Severe Alzheimer’s Disease: A Subgroup Analysis in Patients Already Taking or Not Taking Concomitant Memantine

Abstract

Background/Aims: A large multicenter trial of donepezil 23 mg/day versus donepezil 10 mg/day for moderate-to-severe Alzheimer’s disease allowed patients taking concomitant memantine. We evaluated the efficacy/safety of donepezil 23 and 10 mg/day in this trial, with respect to concomitant memantine use. Methods: Prespecified analysis of data from a 24-week, randomized, double-blind trial. Patients were randomized to donepezil doses (23 vs. 10 mg/day) and stratified by concomitant memantine use (yes or no). Efficacy and safety were assessed for each donepezil dose in subgroups taking or not taking concomitant memantine. Results: At week 24, donepezil 23 mg/day provided significant cognitive benefits over 10 mg/day (p < 0.01) on the Severe Impairment Battery, with or without concomitant memantine (ANCOVA adjusted for baseline score, country and treatment). The higher dose showed no benefit on the global function, Mini-Mental State Examination or activities of daily living measures in either memantine subgroup. Rates of treatment-emergent adverse events (AEs) were higher for donepezil 23 mg/day with memantine (80.7%) than 23 mg/day without memantine (69.7%) or 10 mg/day with/without memantine (66.7/62.0%); across all treatment groups, most events were mild/moderate in severity. Individual rates of serious AEs were low (<1.0%), regardless of concomitant memantine use. Conclusion: In this population, concomitant memantine use did not alter the response profile of donepezil 23 vs. 10 mg/day. Donepezil 23 mg was generally safe and well tolerated among patients receiving donepezil alone and among patients receiving a combination of donepezil and memantine therapy.