Differential efficacy of treatment with acetylcholinesterase inhibitors in patients with mild and moderate Alzheimer's disease over a 6-month period

There are various anticholinesterase inhibitors (AChEIs) for the symptomatic treatment of mild to moderate Alzheimer's disease (AD). All AChEIs have shown greater efficacy than placebo in randomized, double-blind, parallel-group clinical trials. No differential studies have yet been made of the efficacy between all AChEIs. The study aims to determine the differential efficacy of the AChEIs with respect to a historical sample of patients with AD that were not treated with AChEIs. An open-label, prospective, observational study with a retrospective control group was undertaken to examine the evolution of the cognitive function over a 6-month period. The patients were assessed with the Mini-Mental State Examination (MMSE) at study entry and at 6 months. A general linear model was applied for repeated measurements with the MMSE score as the dependent variable, treatment type as an independent variable and the severity of the deterioration, age and the MMSE baseline score as covariables. Of the sample of 147 patients, 40 initiated treatment with donepezil, 32 with galantamine, 30 with rivastigmine and 45 were part of a historical sample of the memory clinic patients between 1991 and 1996 that had not been treated with AChEIs. The average age was 73.7 years (SD = 6.9; range = 52-86), 67.3% were women, 78.2% of the cases were mild and the MMSE baseline score was 18.1 points (range = 11-27). No significant intergroup differences were observed in these variables. The average doses of donepezil, galantamine and rivastigmine were 5.87 mg/day (SD = 1.92), 14.81 mg/day (SD = 6.25) and 6.41 mg/day (SD = 1.82), respectively. At 6 months, the difference in the MMSE score with respect to the untreated group was 1.6 points for donepezil (95% CI 0.79-2.37; p < 0.001), 0.99 points for galantamine (95% CI 0.14-1.85; p = 0.01) and 0.90 points for rivastigmine (95% CI 0.05-1.74; p = 0.03). No significant differences were observed in the efficacy among the groups treated with AChEIs (p > 0.05). Treatment with AChEIs significantly delays the global cognitive impairment associated with AD for at least 6 months. Our study found no significant differences in efficacy between donepezil, galantamine and rivastigmine. Further studies in the context of daily clinical practice will determine the clinical significance of the changes observed. An important variability of the response to the treatment was observed in treated patients.