Effectiveness of open-label donepezil treatment in patients with Alzheimer's disease discontinuing memantine monotherapy

Objective: To evaluate the efficacy and safety of donepezil in patients with Alzheimer's disease (AD) who discontinue memantine due to a lack of efficacy or not being well tolerated. Methods: This study enrolled patients with moderate-to-severe AD (Mini-Mental State Examination [MMSE] score 5-17) who had a history of treatment with memantine monotherapy (10 mg/BID) for ! 3 months prior to screening and maintained until study baseline. For inclusion in this study, the patient's memantine treatment had to have been judged as lacking efficacy or not well tolerated at the screening visit. Information on previous memantine use was also obtained with regard to dose and duration of treatment. At the baseline visit, patients were switched to open-label donepezil 5 mg/day for 4 weeks, and 10 mg/day thereafter. The primary efficacy measure was a change in MMSE at week 12 using a last observation carried forward (LOCF) analysis. Secondary measures included Physician and Caregiver Satisfaction Questionnaires (PSQ, CSQ), the Clinical Global Impression-Improvement (CGI-I), Neuropsychiatric Inventory (NPI), and a Caregiver Diary (CD). Results: At week 12-LOCF, MMSE scores increased by a mean of 1.55 points from baseline (p < 0.0001). At end point, the PSQ and CSQ indicated consistent improvements in satisfaction/ease of use with donepezil; 60.2% of patients improved on the CGI-I; and 44.4-55.6% improved on each of three components of the CD. Improvements on the MMSE, CSQ, and CGI-I were apparent, irrespective of previous cholinesterase (ChE) inhibitor use. No significant effects were seen for the total score on the NPI. Withdrawal rates (8.7% due to adverse events [AEs]) and AEs were consistent with the known donepezil safety profile. Conclusion: Donepezil was effective and well tolerated in moderate-to-severe AD patients who discontinued memantine monotherapy, including those with previous exposure to ChE inhibitors.