Efficacy and safety of rivastigmine in patients with Alzheimer's disease who failed to benefit from treatment with donepezil

Background: Selective acetylcholinesterase (AChE) and dual acetyl- and butyrylcholinesterase inhibitors constitute the only approved agents for the symptomatic treatment of Alzheimer's disease (AD). Donepezil is a specific, reversible inhibitor of AChE, while rivastigmine is a slowly reversible (pseudoirreversible) dual cholinesterase (ChE) inhibitor, with brain-regional specificity for the cerebral cortex and hippocampus. According to the European Marketing Authorisations, the clinical benefit of ChE inhibitors should be reassessed on a regular basis and discontinuation should be considered when evidence of a therapeutic effect is no longer present. However, substantial differences in the pharmacological and pharmacokinetic profiles of the available ChE inhibitors suggest that it may be desirable to switch between ChE inhibitors if patients fail to show efficacy, deteriorate or are unable to tolerate their initially prescribed medication. Design: This open-label, six-month study evaluated the efficacy and safety of rivastigmine in 382 AD patients who had previously failed to benefit from treatment with donepezil 80% to due to lack of efficacy, 11 % due tolerability problems, 9% both reasons). Results: At the end of the study, 56.2% of patients were responders to rivastigmine, as assessed using a global function scale (the Clinicians' Global Impression of Change). Cognitive performance (measured by the Mini-Mental State Examination) and the ability to perform activities of daily living (measured by the Instrumental Activities of Daily Living scale) were improved/stabilised in 48.9% and 57.0% of patients, respectively. Rivastigmine was generally well tolerated, the most common adverse events being nausea and vomiting, consistent with reports from previous clinical studies. The occurrence of side-effects or lack of efficacy with donepezil treatment was not a predictor of similar problems when treated with rivastigmine. Conclusion: Rivastigmine treatment appears to be beneficial in AD patients who have previously failed to benefit from, or were unable to tolerate treatment with, donepezil.