Rivastigmine for Alzheimer's disease: Canadian interpretation of intermediate outcome measures and cost implications

Background: Clinical studies have shown that patients with Alzheimer's disease (AD) who are treated with rivastigmine have statistically significantly better scores on 5 scales used to assess AD than control patients receiving placebo. However, the clinical meaning and cost implications of these differences are not clear. Objective: The purpose of this study was to assess the clinical meaning and cost implications of statistically significant results obtained in clinical trials of rivastigmine for the treatment of AD. Potential cost implications for the health care system, caregivers, and society are considered. Methods: Data on clinical effects of rivastigmine were obtained from published North American and European clinical studies of patients with mild to moderately severe AD receiving rivastigmine 6 to 12 mg/d (n = 828) or placebo (n = 647). Differences in scores on the Alzheimer's Disease Assessment Scale-Cognitive Function, Clinician's Interview-Based Impression of Change with both clinical and caregiver information considered, Progressive Deterioration Scale, Mini-Mental State Examination (MMSE), and Global Deterioration Scale were assessed. A convenience panel of 9 Canadian specialists experienced in the treatment of AD provided their opinions on the clinical importance of the trial results. Chart review was performed to identify specific behaviors that improved, and cost implications of improvements were assessed. Results: The panel determined that statistically significant differences in scores on all scales except the MMSE were likely associated with functional or cognitive differences that were clinically relevant for patients, reflecting stabilization that would have beneficial consequences for caregivers and health care resource use. Subsequent chart review showed that improvement on specific scale items confirmed the physician panel's opinion. Analysis of possible cost implications to society indicated that medication expenditures would be offset largely by delays in the need for paid home care and institutionalization, positive effects on caregiver health, and less time lost from work for the caregiver. Conclusions: From the perspective of a Canadian specialist panel, rivastigmine treatment for AD produces clinically relevant effects for patients that are beneficial to caregivers. These effects suggest decreased use of caregiver resources and delays in the need for institutionalization, both of which reduce societal costs.