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Cytarabine (Ara C, cytosine arabinoside)

Find out what cytarabine is, how you have it and other important information about having cytarabine.

Cytarabine, sometimes called cytosine arabinoside, is a chemotherapy drug and is also known by its brand name, Ara C.

It is a treatment for:

  • acute leukaemias (cancers of the blood)
  • some lymphomas (cancers of the lymph glands)

For some types of lymphoma you have cytarabine injected into the fluid around the spinal cord (intrathecally).

How it works

This drug is a type of chemotherapy drug called an anti metabolite.

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 it

You have cytarabine as an injection into your bloodstream (intravenously) or by injection just under the skin (subcutaneously).

Drugs into your bloodstream

You have the treatment through a drip into your arm or hand. A nurse puts a small tube (a cannula) into one of your veins and connects the drip to it.

You might need a central line. This is a long plastic tube that gives the drugs into a large vein, either in your chest or through a vein in your arm. It stays in while you’re having treatment, which may be for a few months.

Subcutaneous injection

You usually have injections under the skin (subcutaneous injection) into the stomach or thigh. You might have stinging or a dull ache for a short time after this type of injection. The skin in the area may go red and itchy for a while.

When you have it

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. 


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

Side effects

Important information

Other medicines, foods and drink

Cancer drugs can interact with some other medicines and herbal products. Tell your doctor or pharmacist about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies.

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.

Loss of fertility

It is not known whether this treatment affects fertility in people. Talk to your doctor before starting treatment if you think you may want to have a baby in the future.


Don’t breastfeed during this treatment because the drug may come through into your breast milk.

Treatment for other conditions

Always tell other doctors, nurses, pharmacists or dentists that you’re having this treatment if you need treatment for anything else, including teeth problems.


Don’t have immunisations with live vaccines while you’re having treatment and for up to 12 months afterwards. The length of time depends on the treatment you are having. Ask your doctor or pharmacist how long you should avoid live vaccinations.

In the UK, live vaccines include rubella, mumps, measles, BCG, yellow fever and the shingles vaccine (Zostavax).

You can:

  • have other vaccines, but they might not give you as much protection as usual
  • have the flu vaccine (as an injection)
  • be in contact with other people who have had live vaccines as injections

Avoid close contact with people who have recently had live vaccines taken by mouth (oral vaccines) such as oral polio or the typhoid vaccine.

This also includes the rotavirus vaccine given to babies. The virus is in the baby’s poo for up to 2 weeks and could make you ill. So avoid changing their nappies for 2 weeks after their vaccination if possible. Or wear disposable gloves and wash your hands well afterwards.

You should also avoid close contact with children who have had the flu vaccine nasal spray if your immune system is severely weakened. 

More information about this treatment

For further information about this treatment go to the electronic Medicines Compendium (eMC) website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

Information and help

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