A 26-week randomized, double-blind, placebo-controlled, parallel-group study was conducted in the United States to evaluate the efficacy and safety of rivastigmine for patients with Alzheimer’s disease. A total of 699 patients, between 45 and 90 years of age, with mild to moderately severe probable Alzheimer’s disease (mean baseline Mini-Mental State Examination score = 19.7) were randomly assigned to treatment with rivastigmine 6-12 mg/d (n = 231), rivastigmine 1-4 mg/d (n = 233), or placebo (n = 235).

Patients receiving placebo continuously deteriorated over the 26-week period; the mean change from baseline on the Alzheimer’s Disease Assessment Scale–Cognitive Subscale (ADAS-Cog) was 4.15 points.

In contrast, the ADAS-Cog scores of patients in the rivastigmine 6-12 mg group improved over the same period compared with baseline values. At each evaluation point (weeks 12, 18, 26), the mean changes from baseline scores of the ADAS-Cog for patients receiving rivastigmine 6-12 mg/d were statistically significant when compared with those receiving placebo (P<.05).

The treatment with rivastigmine showed a greater benefit in the 6-12 mg/d group, when compared with the 1-4 mg/d group.

At study end point, improvements of 4 points on the ADAS-cog were observed in approximately 25% of patients receiving 6–12 mg/day rivastigmine, compared with only 16% of patients receiving placebo.