Caregivers should watch first for nausea, diarrhea, insomnia, vomiting, muscle cramps, fatigue, and decreased appetite. They should also respond promptly to fainting, suspected stomach bleeding, seizures, or other sudden changes. Aricept is the brand name for donepezil, a medicine approved for mild, moderate, and severe dementia of the Alzheimer's type. It is not approved for every kind of dementia, according to the February 2025 DailyMed/NLM prescribing information.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- Common effects to monitor
- Warning signs that need prompt attention
- Why the dose matters
- Who may need closer observation
- How to separate evidence from rare reports
Common effects to monitor
The most common effects seen in clinical trials were nausea, diarrhea, insomnia, vomiting, muscle cramps, fatigue, and decreased appetite. These problems deserve especially close attention when treatment begins or the dose increases, the DailyMed/NLM label advises. A person with dementia may not describe nausea, poor sleep, or cramps clearly.
Caregivers can instead watch for unfinished meals, repeated bathroom visits, nighttime wakefulness, unusual tiredness, or visible discomfort. Record when each change began, how often it occurs, and whether it interferes with eating, sleep, or daily activity. That timeline helps the prescriber judge whether the change may relate to treatment.
Warning signs that need prompt attention
Donepezil can slow the heart rate or cause heart block, meaning disruption of the heart's electrical signals. It has also been associated with fainting, even in people without a known electrical-conduction problem. Contact the prescriber promptly after any fainting episode. Donepezil can also increase stomach acid.
Watch for possible symptoms of an ulcer or gastrointestinal bleeding, especially if the person has had ulcers or takes aspirin or a nonsteroidal anti-inflammatory drug, commonly called an NSAID. The DailyMed/NLM safety warnings identify both heart and gastrointestinal risks. Seek urgent medical help when fainting causes an injury, bleeding is suspected, or a seizure occurs. Note what happened, when it started, and which medicines the person had taken.
Why the dose matters
Stomach-related side effects occurred more often with the 23-mg dose than with 10 mg in a controlled trial. Nausea affected 11.8% of participants taking 23 mg and 3.4% taking 10 mg. Vomiting affected 9.2% and 2.5%, respectively.
These effects were often temporary, but that does not make them harmless. Repeated vomiting or persistent appetite loss should be reported, particularly after a dose increase. Weight also deserves regular attention. In the same comparison, 8.4% of people taking 23 mg lost at least 7% of their starting weight, compared with 4.9% taking 10 mg, according to the dose-specific DailyMed/NLM trial data.
Who may need closer observation
Tell the prescriber if the person has asthma or obstructive lung disease, because donepezil requires caution in these conditions. Also report new difficulty passing urine; medicines in this class may contribute to bladder-outflow obstruction. Generalized convulsions are another potential class effect, although Alzheimer's disease itself can also cause seizures.
That overlap means a seizure cannot automatically be blamed on donepezil and still requires medical assessment. The complete medicine list matters as well. Make sure the prescriber knows about aspirin, NSAIDs, and any history of ulcers before treatment begins or the dose changes.
How to separate evidence from rare reports
Reports submitted after approval have included heart block, QTc prolongation, torsade de pointes, convulsions, hallucinations, and liver inflammation. QTc prolongation and torsade de pointes are serious disturbances of the heart's rhythm.
These voluntary reports cannot show how frequently an event occurs or prove that donepezil caused it. Caregivers should still report a sudden hallucination, seizure, fainting episode, or other major change rather than trying to determine the cause alone. Keep a brief daily record during treatment changes: Bring the record and the full medicine list to the prescriber instead of changing the dose without medical guidance.
- Dose and time taken
- Appetite and approximate food intake
- Vomiting or diarrhea
- Sleep disruption
- Muscle cramps or unusual fatigue
