Background: Cholinesterase inhibitors (ChEIs) represent the mainstay of symptomatic treatment in Alzheimer's disease. Three medications belonging to this class are presently widely available. These agents differ in their individual mechanisms of action and pharmacokinetic properties. Switching ChEIs can be a reasonable option in cases of intolerance or lack of clinical benefit.
Methods: A systematic literature search of switching ChEIs was conducted, and all studies specifically evaluating this issue were identified. Published consensus guidelines were also searched for recommendations on ChEI switching.
Results: Eight clinical studies are summarized and discussed. All of these studies are open-label or retrospective and they cannot be readily compared because of heterogeneity in design, number of patients, agents used, and endpoints. Switching in most of these studies was done for both “lack of benefit” or “loss of response” after up to 29 months of treatment. Nevertheless, the majority of studies did not include individuals switched for lack of response after several years of treatment. Lack of satisfactory response or intolerance with the initial agent was not predictive of similar results with the second agent.
Conclusions: In light of these findings, we propose the following practical approach to switching ChEIs: (1) in the case of intolerance, switching to a second agent should be done only after the complete resolution of side-effects following discontinuation of the initial agent; (2) in the case of lack of efficacy, switching can be done overnight, with a quicker titration scheme thereafter; (3) switching ChEIs is not recommended in individuals who show loss of benefit several years after initiation of treatment.