Donepezil-Induced Complex Multimodal Hallucinations: Two Cases and a Review of the Literature

Hallucinations are common in neurodegenerative dementias, being present in a significant proportion of patients. Most of the available studies show that acetylcholinesterase inhibitors may be beneficial in preventing and treating hallucinations in patients with neurodegenerative and even psychiatric disorders, even though there are reports that they might also develop as an adverse effect of such therapy. However, a clear causal relationship for the latter association was not previously established. Here we describe 2 cases of patients treated with donepezil who developed complex multimodal hallucinations, which could be causally linked to the drug by means of a challenge-dechallenge (and rechallenge in one case) paradigm. We also provide a narrative review of the literature regarding donepezil and hallucinations and propose a hypothesis to explain the occurrence of this phenomenon.