Combination therapy with cholinesterase inhibitors and memantine for Alzheimer's disease: a systematic review and meta-analysis

Benefits and risks of add-on therapies for Alzheimer's disease

Despite three decades of intensive research, the efforts of scientific society and industry and the expenditures, numerous attempts to develop effective treatments for Alzheimer's disease have failed. Currently, approved and widely used medications to treat cognitive deficits in Alzheimer's disease are symptomatic only and show at best modest efficacy. In this context, the need to develop a successful, disease-modifying treatment is loudly expressed. One way to achieve this goal is the use of add-on therapies or various combinations of existing ‘conventional’ drugs. Results of several clinical studies and post hoc analyses of combination therapy with all cholinesterase inhibitors and memantine are published. Moreover, there is a need for studies on long-term efficacy of combination therapy in Alzheimer's.

Protection against Brain Atrophy by Anti-dementia Medication in Mild Cognitive Impairment and Alzheimer's Disease: Meta-Analysis of Longitudinal Randomized Placebo-Controlled Trials

BACKGROUND

There has not been conclusive evidence for prevention of brain atrophy by anti-dementia drugs in mild cognitive impairment and Alzheimer's Disease.

METHODS

Relevant studies were identified through searches of PubMed, databases of the Cochrane Library, and PsycINFO citations up to 16 May, 2015. Only double-blind, randomized, placebo-controlled clinical trials of anti-dementia drugs in patients with mild cognitive impairment or Alzheimer's Disease were included. Primary outcomes were annualized percent change of total brain volume (%TBV/y), annualized percent change of hippocampal volume (%HV/y), and annualized percent change of ventricular volume (%VV/y) measured by magnetic resonance imaging. Standardized mean difference (SMD) and 95% confidence intervals (CI) were calculated for relevant outcomes.

RESULTS

Seven randomized, placebo-controlled clinical trials (n=1708) were found to meet the inclusion criteria, including 4 mild cognitive impairment studies (n=1327) and 3 Alzheimer's Disease studies (n=381) [3 donepezil studies (2 mild cognitive impairment studies and 1 Alzheimer's Disease study), 1 galantaime study for mild cognitive impairment, 2 mementine studies for Alzheimer's Disease, and 1 rivastigmine study for mild cognitive impairment]. Pooled anti-dementia drugs showed superior protective outcomes compared with placebo regarding %TBV/y (SMD=-0.21, 95%CI=-0.37 to -0.04, P=.01, N=4, n=624) and %VV/y (SMD=-0.79, 95%CI=-1.40 to -0.19, P=.01, N=3, n=851). However, %HV/y failed to show difference between both groups. Among anti-dementia drugs, donepezil showed significantly greater protective effects than placebo regarding %TBV/y (SMD=-0.43, 95%CI=-0.74 to -0.12, P=.007, N=1, n=164) and %VV/y (SMD=-0.51, 95%CI=-0.73 to -0.29, P<.00001, N=2, n=338). Rivastigmine was also superior to placebo regarding %VV/y (SMD=-1.33, 95%CI=-1.52 to -1.14, P<.00001).

CONCLUSIONS

The results favored the hypothesis that anti-dementia drugs may prevent brain atrophy in patients with mild cognitive impairment and Alzheimer's Disease.