1. About donepezil

Donepezil is a medicine that helps with some types of dementia.

It does not cure dementia. However, it treats some of the symptoms of Alzheimer's disease, Parkinson's disease or dementia with Lewy bodies.

It can also help with "mixed dementia". This is when you have more than one type of dementia.

Donepezil is available on prescription only.

It comes as tablets, including tablets that melt in your mouth, and as a liquid that you drink.

2. Key facts

  • Donepezil can help with symptoms like being forgetful or confused.
  • The most common side effects of donepezil are diarrhoea, headache and feeling sick (nausea).
  • You can take it with or without food.
  • Drinking alcohol stops donepezil from working as well as it should. It also increases the risk of side effects.

3. Who can and cannot take donepezil

Donepezil can be taken by adults only.

Donepezil is not suitable for some people. To make sure this medicine is safe to take, tell your doctor if you or the person you're caring for have:

  • had an allergic reaction to donepezil or other medicines in the past
  • liver problems
  • ever had an ulcer in your gut or intestines, or a stomach ulcer
  • heart problems, such as an irregular or slow heartbeat
  • asthma or other lung disease such as COPD
  • ever had a seizure or fit
  • a condition that makes it difficult to pee

4. How and when to take it

It's best to take your donepezil at bedtime. This is because you may feel dizzy after you take it.

If donepezil gives you bad dreams or makes it hard to sleep, you can take it in the morning instead.


Always follow the instructions that come with your medicine.

Donepezil comes as 5mg or 10mg tablets.

If you are taking liquid donepezil, a 5ml spoonful contains 5mg of medicine (1mg/1ml).

The usual starting dose of donepezil is 5mg (one tablet or one 5ml spoonful of liquid), taken once a day.

After a month, the doctor may increase your dose to 10mg (one 10mg tablet or two 5ml spoonfuls of liquid), taken once a day.

How to take the tablets

Swallow the tablets with a drink of water.

Donepezil also comes as a tablet that melts in your mouth (called an "orodispersible" tablet).

Put the tablet on your tongue and let it dissolve. You can then swallow it without a drink. You can have a drink of water afterwards if you want to.

How to take the liquid

Use the plastic spoon that comes with your medicine to measure out your dose. If you do not have a measuring spoon ask a pharmacist for one. Do not use a kitchen teaspoon as it will not give the right amount.

Swallow the liquid donepezil. You can have a drink of water afterwards if you like.

What if I forget to take it?

If you forget a dose of donepezil, skip the missed dose and take the next one at the normal time the next day.

Do not take a double dose to make up for a forgotten dose.

If you've forgotten to take your donepezil for more than a week, talk to your doctor before you take any more.

If you forget doses often, it may help to set an alarm to remind you. You could also ask a doctor, pharmacist or dementia support group for advice on other ways to help you remember to take your medicine.

What if I take too much?

The amount of donepezil that can cause an overdose varies from person to person.

If you need to go to A&E, do not drive yourself. Get someone else to drive you or call for an ambulance.

Take the donepezil packet, or the leaflet inside it, plus any remaining medicine with you.

5. Side effects

Like all medicines, donepezil can cause side effects, although not everyone gets them.

Side effects are less likely to happen if your doctor starts you on the lower 5mg dose for at least a month.

Common side effects

The most common side effects of donepezil happen in more than 1 in 100 people.

Talk to your doctor or pharmacist if these side effects bother you or do not go away:

  • diarrhoea
  • feeling sick (nausea)
  • headache
  • feeling sleepy in the daytime or feeling dizzy

Serious side effects

Less than 1 in 100 people have serious side effects with donepezil.

Call a doctor straight away if you, or the person you're caring for, have:

  • yellow skin or the whites of your eyes turn yellow, or if you have pale poo and dark pee – these can be signs of liver problems
  • severe indigestion, heartburn or stomach pain, severe or continued vomiting – these can be signs of an ulcer in your stomach or gut
  • black poo, or blood or something that looks like coffee grounds in your vomit – these can be signs of internal bleeding
  • muscle weakness or cramps and pains in your muscles (that you did not have before) – these can sometimes be signs of muscle and kidney problems
  • high temperature together with stiff muscles, sweating, confusion and seeing or hearing things that are not there – these can be signs of a rare side effect (called neuroleptic malignant syndrome)

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to donepezil.

These are not all the side effects of donepezil. For a full list see the leaflet inside your medicines packet.


You can report any suspected side effect to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • diarrhoea – drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark strong-smelling pee. Do not take any other medicines to treat diarrhoea, including rehydration salts, without first speaking to a pharmacist or doctor
  • feeling sick – it may help to avoid eating very rich, fatty or spicy food
  • headache – make sure you rest and drink plenty of fluids. If it's bothering you, ask a pharmacist to recommend a painkiller. Talk to a doctor if your headaches last longer than a week or are severe
  • feeling sleepy in the daytime or feeling dizzy – try taking your medicine at night. If you feel dizzy or tired do not drive or ride a bike until you feel more alert. Talk to a doctor if these effects bother you, or do not get better

As your body gets used to donepezil, these side effects should wear off. If you are still bothered by them after a week or two, speak to a doctor. They may want to adjust your dose or recommend a different medicine.

7. Cautions with other medicines

Some medicines do not mix well with donepezil. They can increase the risk of side effects or stop donepezil working as well as it should.

Tell your doctor if you or the person you're caring for:

These are not all the medicines that interfere with donepezil.

For a full list, see the leaflet inside your medicines packet.

Taking donepezil with painkillers

It is usually OK to take paracetamol with donepezil.

Do not take anti-inflammatory painkillers (NSAIDs), such as aspirin or ibuprofen, without checking with a doctor first.

Mixing donepezil with herbal medicines and supplements

St John's wort can lower the levels of donepezil in your blood. This can stop your medicine from working as well as it should.


Tell a doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

8. Common questions

Page last reviewed: 19/02/2020
Next review due: 19/02/2023