Duration of therapy with acetylcholinesterase inhibitors in patients with mild-to-moderate Alzheimer's disease as reported in the literature.

Objective: To review the literature regarding the treatment duration of acetylcholinesterase inhibitor (AChEI) therapy for mild-to-moderate Alzheimer's disease (AD) patients.
Data Sources: A literature search was performed using MEDLINE/PubMed, Embase, International Pharmaceutical Abstracts, and Clinical Key (all through May 31, 2013) with the search terms Alzheimer's disease, cholinesterase inhibitors, dementia, treatment and duration, with limits to human, clinical, and observational trials, and English studies; no limits were placed on publication dates.
Study Selection and Data Extraction: Based on the study selection, 40 studies were identified. The criteria for studies reviewed focused on the duration of AChEIs in patients with mild or moderate AD for a minimum of one year.
Data Synthesis: Based on the selection criteria, five studies were reviewed. These studies evaluated the cognitive efficacy of AChEI after "long-term" (1.5 years) treatment in the clinical trial with follow-up noted in the observational studies of a maximum of "greater than 3 years" (up to 7 years). Cognitive decline was measured by changes in Mini-Mental State Exam scores or Alzheimer's Disease Assessment Scale scores. There were no studies identified that suggested an optimal duration of AChEI therapy for AD patients.
Conclusion: Based on the trials reviewed, the duration for AChEI use is very patient-specific; therefore, risk versus benefit of therapy needs to be evaluated regularly in AD patients. The maximum mean duration of follow-up in the clinical study analyzed here was only 1.5 years and observational studies with follow-up "greater than 3 years." Further long-term research is needed.