Abstract
Objective: To explore the effects of extended-release (ER) memantine (28 mg, once daily) on outcome measure combinations in the subset of Alzheimer’s disease (AD) patients receiving donepezil during the MEM-MD-50 trial (NCT00322153). Background: The efficacy of memantine ER was demonstrated in the 24-week, randomized, double-blind, placebo-controlled, parallel-group trial, MEM-MD-50 (placebo, n=335; memantine, n=342) in patients with moderate to severe AD concurrently taking a cholinesterase inhibitor. Design/Methods: Efficacy outcomes included measures of cognition (SIB), function (ADCS-ADL19), behavior (NPI), and global status (CIBIC-Plus). In this post hoc analysis, two levels of response were defined for each measure: improvement or stabilization (“no decline”; baseline-to-endpoint improvement of ≥0 points for the SIB, ADCS-ADL19, and NPI; endpoint score ≤4 for CIBIC-Plus) and clinically notable response (baseline-to-endpoint improvement of ≥3 points for the SIB, ADCS-ADL19, and NPI; endpoint score ≤3 for CIBIC-Plus). Treatment groups were compared by calculating the proportions of patients who achieved no decline or a clinically notable response on any combination of 2, 3, or all 4 efficacy measures. Data were analyzed using observed cases and Wald’s test (α=0.05); numbers needed to treat (NNTs) were also calculated. Due to the exploratory nature of this analysis, no corrections for multiple comparisons were performed. Results: In patients receiving donepezil, the proportions of responders in the memantine ER group (n=187) exceeded those in the placebo group (n=184) for both response levels and all outcome combinations, except for the ADCS-ADL19 (≥3 points) in which responder proportions were almost identical. The difference between proportions of memantine ER- and placebo-treated patients who experienced no decline was significant for the SIB/CIBIC-Plus combination (62.0% vs 50.8%; P=0.0240, NNT=9). Conclusions: This exploratory post-hoc analysis suggests that, in patients with moderate to severe AD receiving donepezil, memantine ER provides simultaneous benefits on multiple clinical domains, especially stabilization of cognition and global status.