Cytarabine (Ara C, cytosine arabinoside) | Cancer Research UK
Cancer Research UK on Google+ Cancer Research UK on Facebook Cancer Research UK on Twitter

What cytarabine is

Cytarabine is a treatment for acute leukaemias (cancers of the blood) and some lymphomas (cancer of the lymph glands).


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 kill cancer cells by stopping them making and repairing DNA that they need to grow and multiply.


How you have cytarabine

Cytarabine is a clear liquid. You have it as a drip into a vein (intravenous infusion) or by injection just under the skin (subcutaneously).

Cytarabine as a drip into a vein 

You can have it through a thin, short tube (a cannula) put into a vein in your arm. 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 before or during your course of treatment and it stays in place as long as you need it.

You can read our information about having cancer drugs.

Having cytarabine through a drip can take from 10 minutes to 2 hours, depending on the dose you have. You may have it every day for 10 days. Or you may have it for 5 days and then have a rest of 2 to 9 days before repeating the treatment. 

Cytarabine as an injection under the skin

You can have cytarabine as an injection just under the skin. Look at our video about having an injection just under the skin.

Cytarabine into spinal fluid

For some types of lymphoma you have cytarabine injected into the fluid around the spinal cord. The side effects are different to those caused by cytarabine into the bloodstream or under the skin. 

Read about cytarabine into spinal fluid.


Tests during treatment

You have blood tests before starting treatment and regularly during your treatment. The tests check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.


About side effects

We've listed the side effects associated with cytarabine. You can use the links to find out more about each side effect. Where there is no link, please go to our information about cancer drug side effects or use the search box at the top of the page.

You may have a few side effects. They may be mild or more severe. A side effect may get better or worse through your course of treatment. Or more side effects may develop 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)

The side effects may be different if you are having cytarabine with other medicines.

Tell your doctor, nurse or pharmacist straight away if any of the side effects get severe.


Common side effects

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

  • Fatigue (tiredness) during and after treatment – most people find their energy levels are back to normal after 6 months to a year
  • Soreness at the injection site (if you are having injections under the skin)
  • Women may stop having periods (amenorrhoea) but this may only be temporary

Occasional side effects

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

  • 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. If you have a severe infection this can be life threatening. Contact your treatment centre straight away if you have any of these effects or if your temperature goes above 38°C
  • 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, or bleeding gums after brushing your teeth. Or you may have lots of tiny red spots or bruises on your arms or legs (known as petechiae)
  • 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
  • Loss of fertility – you may not be able to become pregnant or father a child after this treatment. Talk to your doctor before starting treatment if you think you may want to have a baby in the future. Men may be able to store sperm before starting treatment
  • 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
  • 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
  • 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 ends

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.


Rare side effects

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


Side effects of high dose treatment

Treatment with high doses can cause the following side effects

  • Sore, red skin, particularly on the hands and feet
  • Drowsiness and confusion – 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)
  • Temporary red and sore eyes with sensitivity to light and eyesight changes – your doctor or nurse may give you steroid eye drops to help prevent this
  • Some people have watery eyes
  • To and fro movements of the eyes (nystagmus)

Important points to remember

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.

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 at least 6 months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


Don't breastfeed during this treatment because the drug may come through in the breast milk.


Immunisations and chemotherapy

You shouldn't 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


More information about cytarabine

This page doesn't 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

Rate this page:
Submit rating


Rated 4 out of 5 based on 23 votes
Rate this page
Rate this page for no comments box
Please enter feedback to continue submitting
Send feedback
Question about cancer? Contact our information nurse team

No Error

Updated: 22 December 2015