Donepezil commonly causes nausea, diarrhea, trouble sleeping, dizziness, muscle cramps, and vomiting. Caregivers should also watch for fainting, a slow pulse, bleeding, weight loss, breathing problems, seizures, urinary difficulty, or an allergic reaction. Donepezil is a medicine approved for mild, moderate, and severe dementia caused by Alzheimer's disease. It may improve thinking abilities or slow their loss, but it does not cure Alzheimer's disease, according to MedlinePlus.
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 side effects to expect
- When side effects deserve closer attention
- Warning signs that need prompt care
- Bleeding, seizures, and allergic reactions
- What caregivers should record and report
Common side effects to expect
Digestive problems are among the most frequent side effects. In pooled trials involving mild-to-moderate Alzheimer's disease, nausea affected 11% of donepezil users versus 6% taking placebo. Diarrhea affected 10% versus 5%, while vomiting affected 5% versus 3%.
Other reported effects included insomnia, dizziness, and muscle cramps. The FDA-approved ARICEPT label on DailyMed reports insomnia in 9% versus 6% with placebo, dizziness in 8% versus 6%, and muscle cramps in 6% versus 2%. Record when a symptom begins, how often it happens, and whether it disrupts eating, sleep, walking, or daily care. This information can help the prescriber judge the symptom's importance.
When side effects deserve closer attention
Digestive effects can become more likely as the dose rises. In a comparison of 23 mg and 10 mg, nausea occurred in 11.8% versus 3.4% of users. Vomiting occurred in 9.2% versus 2.5%. Watch particularly closely after treatment begins or the dose increases.
repeated vomiting or diarrhea deserves attention because it can interfere with food, fluids, and routine care. Appetite and weight also matter. In one controlled study, 8.4% of people taking 23 mg lost at least 7% of their starting weight, compared with 4.9% taking 10 mg. Keep a consistent weight record and report a clear downward trend or reduced appetite.
Warning signs that need prompt care
Donepezil can slow the heart rate or cause heart block, meaning electrical signals do not move normally through the heart. This can occur even without a known conduction problem.
Seek prompt medical attention for: People with asthma or obstructive lung disease require particular care because donepezil can affect breathing. Do not assume a breathing change is simply part of aging or dementia.
- Fainting
- A noticeably slow pulse
- Chest pain
- New or worsening breathing problems
- Difficulty urinating
Bleeding, seizures, and allergic reactions
Black or tarry stools, red blood in stool, bloody vomit, coffee-ground-like vomit, or worsening stomach pain require urgent medical evaluation. These signs may indicate an ulcer complication or gastrointestinal bleeding. People with previous ulcers or those using nonsteroidal anti-inflammatory drugs, or NSAIDs, need closer monitoring.
Trials of 5 mg and 10 mg did not show more ulcers or gastrointestinal bleeding than placebo, but the 23-mg trial found higher rates than with 10 mg. Seizures and serious allergic reactions are uncommon but urgent warning signs. Seek urgent care for seizure activity or signs of a serious allergic reaction, as advised by the NHS donepezil safety guidance. A seizure does not prove donepezil caused it, because seizures can also occur with Alzheimer's disease.
What caregivers should record and report
A short symptom log can make a medical conversation more precise. Include: For fainting, a slow pulse, chest pain, possible bleeding, worsening breathing, a seizure, or a serious allergic reaction, seek medical care promptly instead of waiting for the next routine appointment.
- The symptom and when it started
- The current donepezil dose and any recent increase
- Vomiting or diarrhea episodes
- Appetite changes and recorded weight
- Fainting, pulse changes, chest pain, or breathing trouble
