Monday Pharmaceutical Mystery: May 11


Can donepezil be the cause of abnormal dreams?

Mrs. Jones stops by your pharmacy and asks to speak to the pharmacist. She tells you that ever since her father started taking donepezil (Aricept, Eisai), he has had strange dreams. Mrs. Jones wants to know if the dreams could be due to the donepezil.

Mystery: Can donepezil be the cause of abnormal dreams?

Solution: It is recommended in the brand manufacturer information that donepezil be taken at night, just prior to going to sleep.1 However, in clinical studies, 3% of patients treated with donepezil experienced abnormal dreams, compared to 0% of patients taking placebo.1

In a retrospective study on the impact of nighttime donepezil dosing on sleep, 186 charts were studied. Of these patients, 103 took donepezil at night. Almost half of the patients who took donepezil at night (47.6%) reported night time disturbances, compared to 25% of patients who took donepezil in the morning.2

Night time disturbances included vivid dreams, nightmares, insomnia, sleep-walking, sleep-talking, and nighttime psychosis. The authors concluded that changing the medication administration to the morning should be attempted before switching medications.2

Another small study explains that acetylcholinesterase inhibitors such as donepezil, while improving cognitive performance, can influence sleep quality, especially in the “quality and amount of dreams.” The researchers noted that when donepezil was taken in the morning, none of the patients had nightmares.

The researchers “suggest that the activation of the visual association cortex during REM sleep is enhanced by donepezil, a mechanism most likely facilitating the development of nightmares in patients with dementia of the Alzheimer type.”3

You advise Mrs. Jones to consult with her father’s prescriber about switching to daytime dosing of donepezil.


  • US National Library of Medicine. Daily Med: Aricept (donepezil). NLM website. Updated December 25, 2018. Accessed May 7, 2020.
  • Agboton C, Mahdavian S, Singh A, et al. Impact of nighttime donepezil administration on sleep in the older adult population: A retrospective study. Mental Health Clinician: September 2014, Vol. 4, No. 5, pp. 257-259 Accessed May 7, 2020.
  • Singer M, et al. Nightmares in patients with Alzheimer's disease caused by donepezil. Therapeutic effect depends on the time of intake. Nervenarzt. 2005 Sep;76(9):1127-8, 1129. Accessed May 7, 2020.

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