Cytarabine (Ara C, cytosine arabinoside) | Cancer Research UK
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Cytarabine (Ara C, cytosine arabinoside)

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This page tells you about the chemotherapy drug cytarabine and its possible side effects. There are sections about


What cytarabine is

Cytarabine is used to treat acute leukaemias and sometimes non Hodgkin lymphoma (NHL).


How cytarabine works

This drug is one of a group of chemotherapy drugs called anti metabolites. Anti metabolites are similar to normal body molecules but they are slightly different in structure. They stop cancer cells making and repairing DNA that they need to grow and multiply.


How you have cytarabine

Cytarabine is a clear liquid. You can have it

Cytarabine through a drip can take from 10 minutes to 2 hours, depending on the dose you have. 

You can have the drug into your bloodstream through a thin, short tube (a cannula) put into a vein in your arm each time you have treatment. Or you may have it through a central line, a portacath or a PICC line. These are long, plastic tubes that give the drugs directly into a large vein in your chest. You have the tube put in just before your course of treatment starts and it stays in place as long as you need it.

You usually have cytarabine chemotherapy as a course of several cycles of treatment. The treatment plan depends on which type of cancer you have. There is information about planning chemotherapy  in the chemotherapy section.

The side effects associated with cytarabine are listed below. You can use the links (underlined) to find out more about each side effect. Where there is no link please look at our cancer drugs side effects section or use the search box at the top of the page.


Common side effects

More than 10 in every 100 people have one or more of the side effects listed below.

A temporary drop in the number of blood cells made by the bone marrow, causing

  • An increased risk of getting an infection from a drop in white blood cells – it is harder to fight infections and you can become very ill. You may have headaches, aching muscles, a cough, a sore throat, pain passing urine or you may feel cold and shivery
  • Tiredness and breathlessness due to a drop in red blood cells (anaemia) – you may need a blood transfusion
  • Bruising more easily due to a drop in platelets – you may have nosebleeds, bleeding gums after brushing your teeth, or lots of tiny red spots or bruises on your arms or legs (known as petechia)

Some of these side effects can be life threatening, particularly infections. Contact your treatment centre straight away if you have any of these effects. Your doctor will check your blood counts regularly to see how well your bone marrow is working.

Other common side effects include

  • Fatigue (tiredness) during and after treatment – most people find their energy levels are back to normal after 6 months to a year
  • Feeling or being sick is usually mild to moderate unless you are having high dose treatment
  • Diarrhoea and tummy (abdominal) pain – if you are going to get this side effect, it usually happens about a week after your treatment
  • A sore mouth or mouth ulcers – if you are going to get this side effect, it usually happens about a week after your treatment
  • Loss of appetite is likely if you have sickness, diarrhoea, or a sore mouth
  • Women may stop having periods (amenorrhoea) but this may only be temporary
  • Loss of fertility – we don’t know exactly how this drug affects your ability to become pregnant or father a child. Talk to your doctor before starting treatment if you may want to have a baby in the future
  • Temporary redness of the eyes with sensitivity to light and eyesight changes
  • Some people have watery eyes
  • Redness and inflammation of the skin, which may be itchy
  • Hair loss
  • High uric acid levels in your blood due to cancer cells being broken down by the body – you will have regular blood tests and will be asked to drink plenty of fluids to flush out the uric acid. You may also have a drug called allopurinol
  • Soreness at the injection site (if you are having injections under the skin)

Occasional side effects

Between 1 and 10 in every 100 people have one or more of these.

  • Aching muscles (myalgia) and bones
  • Inflammation of the covering around the heart (pericarditis) – let your doctor or nurse know if you have any pain in the centre of your chest
  • Headaches
  • Lung infections and breathlessness
  • A sore throat
  • Liver changes that are mild and unlikely to cause symptoms – they will usually go back to normal when treatment is finished, but you will have regular blood tests to check how well your liver is working
  • Dizziness
  • Difficulty passing urine – let your doctor or nurse know straight away if you need to pass urine but nothing will come out
  • Blood clots – let your nurse or doctor know if you have a sore, painful, red area on your leg or sudden chest pain and breathlessness
  • Kidney changes that are mild and unlikely to cause symptoms – they will usually go back to normal when treatment finishes, but you will have regular blood tests to check how well your kidneys are working

Rare side effects

Very rarely people may have an abnormal heart rhythm while having cytarabine treatment. Your doctor and nurses will monitor your heart.


High dose side effects

Treatment with high doses of cytarabine can cause the following side effects

  • Sore, red eyes because some of the drug is removed from your body (excreted) in your tears – your doctor may prescribe steroid eye drops to prevent sore eyes
  • Sore, red skin, particularly on the hands and feet
  • Drowsiness and confusion can affect up to 1 in 10 people (10%) having high dose treatment – this is usually mild and gets better on its own. It is more likely if you are over 40, or have liver or kidney problems
  • Temporary personality changes 
  • Fits (seizures)
  • To and fro movements of the eyes (nystagmus)

A cytarabine syndrome sometimes happens about 6 to 12 hours after having the drug. It is a combination of symptoms including a high temperature, aching muscles, bone pain, occasionally chest pain, a rash, sore eyes, and extreme weakness. Steroids can help to prevent or treat this syndrome.


Important points to remember

You may have 1 or 2 or a few of the side effects mentioned above. They may be mild or more severe. A side effect may get better or worse through your course of treatment. Or you may have more side effects as the course goes on. This depends on

  • How many times you've had the drug before
  • Your general health
  • The amount of the drug you have (the dose)
  • Other drugs you are having

Coping with side effects

Talk to your doctor, pharmacist or nurse about all your side effects so that they can help you manage them. Your nurse will give you a contact number you can ring if you have any questions or problems. They can give you advice or reassure you. If in doubt, call them.

Other medicines

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and over the counter remedies. Some drugs can react together. Cytarabine may stop some other medicines from working so well. These medicines include

  • Digoxin tablets (a heart medicine)
  • An antibiotic called gentamicin
  • A medicine called flucytosine that is used to treat fungal infections

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment with this drug and for a few months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


Breastfeeding is not advisable during this treatment because the drug may come through in the breast milk.


Immunisations and chemotherapy

You should not have immunisations with live vaccines while you are having chemotherapy or for at least 6 months afterwards. In the UK, these include rubella, mumps, measles (usually given together as MMR), BCG, yellow fever and Zostavax (shingles vaccine).

You can have other vaccines, but they may not give you as much protection as usual until your immune system has fully recovered from your chemotherapy. It is safe to have the flu vaccine.

It is safe for you to be in contact with other people who've had live vaccines as injections. There can be problems with vaccines you take by mouth (oral vaccines), but not many people in the UK have these now. So there is usually no problem in being with any baby or child who has recently had any vaccination in the UK. You might need to make sure that you aren't in contact with anyone who has had oral polio, cholera or typhoid vaccination recently, particularly if you live abroad.


Related information

On this website you can read about

acute leukaemias 

non Hodgkin lymphoma (NHL)


More information about cytarabine

This page does not list all the very rare side effects of this treatment that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at

If you have a side effect not mentioned here that you think may be due to this treatment you can report it to the Medicines Health and Regulatory Authority (MHRA) at

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Updated: 17 January 2014