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Managing Donepezil (Aricept) Side Effects: A Practical Guide for UK Family Caregivers

Donepezil, also known as Aricept, is a common medication for Alzheimer's and some other dementias. While it can help with thinking and daily function, it often causes side effects like nausea, diarrhoea, loss of appetite, and sleep changes. This guide explains why these happen, what you can do to manage them at home, and when to call a doctor or 111. You are not alone in this, and there are concrete, gentle steps you can take to help your loved one feel more comfortable.

Key points

  • Donepezil side effects are common but often mild and improve with time; many people have no side effects at all.
  • Always give donepezil with food to reduce nausea and stomach upset.
  • For diarrhoea, focus on fluids – water or squash – and avoid over-the-counter diarrhoea medicines without medical advice.
  • Serious side effects like liver problems, stomach ulcers, or slow heart rate need urgent medical attention – call 111 or a doctor immediately.
  • Never stop donepezil suddenly; always get medical guidance for dose changes or discontinuation.
  • Keep a side effect diary and report any concerns to the GP, pharmacist, or via the UK Yellow Card scheme.

Why Donepezil Causes Side Effects

Donepezil works by increasing levels of a brain chemical called acetylcholine, which helps nerve cells communicate. This boost can improve memory and thinking in some people with dementia. However, acetylcholine also affects other parts of the body, especially the digestive system and the heart. That is why common side effects include nausea, vomiting, diarrhoea, loss of appetite, and sometimes a slow heart rate. These effects are most noticeable when the medication is first started or when the dose is increased, because the body needs time to adjust.

Common Side Effects and What They Look Like

More than 1 in 100 people taking donepezil experience diarrhoea, nausea, vomiting, headache, muscle cramps, difficulty sleeping (insomnia), or unusual dreams. Some people also feel very tired or dizzy. These side effects are usually mild and often improve within a few days or weeks as the body gets used to the medicine. However, they can be distressing for both the person with dementia and the caregiver. It is important to know that not everyone gets side effects, and many people have only minor ones.

Serious Side Effects That Need Urgent Medical Attention

Although rare, donepezil can cause serious problems. Call a doctor or NHS 111 immediately if you notice yellowing of the skin or whites of the eyes (which may be less obvious on black or brown skin), dark urine, pale poo, severe indigestion or stomach pain, severe or ongoing vomiting, black or tarry stools, or vomit that looks like coffee grounds. These can be signs of liver problems, a stomach ulcer, or internal bleeding. Also seek urgent help if the person develops muscle weakness or cramps they did not have before, a high temperature with stiff muscles, sweating, confusion, or seeing or hearing things that are not there. A slow heart rate can cause dizziness, fainting, or falls. If you suspect an overdose, get emergency help immediately – signs include increased watering of the mouth, increased sweating, low blood pressure, muscle weakness, severe nausea or vomiting, slow heartbeat, and trouble breathing.

General caregiving information, not medical advice. Check medications and major care changes with your clinician.

Step-by-step

  1. Give donepezil with a small meal or snack like toast or yoghurt, and offer small, frequent, bland foods throughout the day to ease nausea and poor appetite.

  2. If diarrhoea occurs, encourage regular sips of water, squash, or clear soup, and watch for dark urine, dizziness, or peeing less than usual as signs of dehydration.

  3. For insomnia or vivid dreams, ask the GP about taking donepezil in the morning instead of at bedtime, and build a calming pre-sleep routine with dim lights and gentle music.

  4. Help the person stand or sit slowly when they feel dizzy, and keep the home well-lit and free of clutter to prevent falls.

  5. Keep a simple diary of any side effects — what happened, when, and how bad — and bring it to every appointment to help the GP spot patterns.

  6. If side effects don't settle after a few weeks, ask the GP about a lower dose, a slower titration schedule, or switching to rivastigmine or galantamine.

  7. Tell the GP or pharmacist about every other medicine, supplement, or herbal remedy the person takes, as some can interact with donepezil or worsen side effects.

  8. Report any suspected side effect to the Yellow Card scheme at yellowcard.mhra.gov.uk, even if you're not sure donepezil was the cause.

What not to do

  • Don't give over-the-counter diarrhoea medicines or rehydration salts without first checking with a pharmacist — some can interact with donepezil or make dehydration worse.

  • Don't stop donepezil suddenly because of side effects — abrupt withdrawal can cause a rapid decline in thinking and behaviour. The GP can guide a safe, gradual reduction.

  • Don't assume every new symptom is from donepezil — a fall, new confusion, or sudden drowsiness may signal an infection, dehydration, or another problem that needs proper assessment.

  • Don't ignore fainting, severe dizziness, or unusual tiredness — these can be signs of a slow heart rate, especially in people with existing heart conditions, and warrant a prompt call to the GP or NHS 111.

Practical tools

  • Side Effect Diary Template

    Create a simple chart with columns for date, time, side effect, severity (mild/moderate/severe), and what helped. Keep it by the medication box or in a care notebook so you can spot patterns and share clear information with the GP.

  • Anti-Nausea Snack Box

    Keep a small container of plain crackers, rice cakes, bananas, or dry toast to offer between meals when queasiness strikes. Steer clear of strong-smelling or greasy foods that can worsen nausea.

  • UK Yellow Card Reporting Link

    Bookmark yellowcard.mhra.gov.uk on your phone so you can report any side effect in a few minutes, even if you're unsure donepezil caused it. Every report helps the MHRA keep medicines safe for everyone.

  • Red Flag Symptoms Quick-Reference Card

    A small card for the fridge or wallet listing the serious symptoms that need urgent medical attention: yellowing skin or eyes, very dark urine or pale poo, severe stomach pain, black or bloody stools, fainting or a very slow heartbeat, and seizures. If you spot any, call 999 or go to A&E.

Discuss with your clinician

Ask the doctor: 'Is a lower starting dose (e.g., 2.5 mg) appropriate for my loved one to reduce side effects?'

Ask the pharmacist: 'Could any of the other medicines my relative takes be interacting with donepezil and making side effects worse?'

Ask the specialist: 'If side effects continue, what are the alternatives to donepezil, such as rivastigmine or galantamine?'

Ask the GP: 'Should we consider stopping donepezil if side effects are severe or if the person has advanced dementia? What is the safest way to do that?'

Ask the cardiologist or GP: 'Is it safe for my relative to take donepezil given their history of heart problems or slow heart rate?'

Ask the doctor: 'What signs of overdose should I watch for, and what should I do if I suspect one?'

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