Cytarabine into spinal fluid (intrathecal cytarabine)

Cytarabine is a type of chemotherapy. It is also known as Ara C or cytosine arabinoside.

You pronounce cytarabine sye-ta-ra-bin.

You might have cytarabine injected into the fluid around the spinal cord (cerebrospinal fluid or CSF). This is called intrathecal chemotherapy.

Your doctor gives you the drug during a procedure called a lumbar puncture Open a glossary item. The drug mixes with the cerebrospinal fluid and circulates through the brain.

It is a treatment for:

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

How does cytarabine work?

Cytarabine is a type of chemotherapy drug called an antimetabolite. Open a glossary item It kills cancer cells by stopping them from making and repairing DNA that they need to grow and multiply.

You might have cytarabine into the spinal fluid if there are cancer cells there. You might also have it as prevention, in case cancer cells get into the spinal fluid.  

How do you have cytarabine into the spinal fluid?

Cytarabine is a clear liquid. An experienced cancer doctor injects it into the fluid around the spinal cord during a lumbar puncture.

Intrathecal injection

You have an intrathecal injection of cytarabine the same way you have a lumbar puncture. You lie on your side. Your doctor gives you a small injection to numb an area in your back. They then inject the cytarabine between 2 of your spinal bones into the spinal fluid. It takes from 1 to 5 minutes. Afterwards you need to lie flat for an hour.

Diagram showing how you have a lumbar puncture

You can also have cytarabine as an injection:

  • into your bloodstream (intravenously)
  • just under the skin (subcutaneously)

When do you have cytarabine into the spinal fluid?

The number of treatments may vary. Your doctor will tell you how often you need 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.

What are the side effects of cytarabine into the spinal fluid?

Side effects can vary from person to person. They also depend on what other treatments you're having. 

When to contact your team

Your doctor, nurse or pharmacist will go through the possible side effects. They will monitor you during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

  • you have severe side effects 

  • your side effects aren’t getting any better

  • your side effects are getting worse

Early treatment can help manage side effects better. 

Contact your advice line immediately if you have signs of infection, including a temperature above 37.5C or below 36C.

We haven't listed all the side effects here. Remember it is very unlikely that you will have all of these side effects. But you might have some of them at the same time.

Some of the side effects listed are more likely to happen if you are having cytarabine as a drip or injection into a vein than if you are having it in the spinal fluid.

Common side effects

Common side effects happen in more than 10 in 100 people (more than 10%). At the time of this review, there have been no reports of common side effects for this treatment.

Occasional side effects

These side effects happen in between 1 and 10 out of every 100 people (between 1 and 10%). You might have one or more of them. They include:

Breathlessness and looking pale

You might be breathless and look pale due to a drop in red blood cells. This is called anaemia.

Increased risk of bruising and bleeding

This is due to a drop in the number of platelets in your blood. These blood cells help the blood to clot when we cut ourselves. 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).

Eye problems

You might have eye problems including burning, sore, red, itchy eyes (conjunctivitis).

You might also have vision problems or your eyes might be more sensitive to light. 

Tell your healthcare team if you have this. They can give you eye drops or other medication to help. 

Inflamed blood vessels

Your blood vessels might get inflamed. Symptoms include red spots on the skin, lumps or sores. Your legs and arms might also feel weak and numb. Contact your advice line or tell your doctor or nurse if you have any of these symptoms. 

High temperature (fever)

If you get a high temperature, let your healthcare team know straight away. Ask them if you can take paracetamol to help lower your temperature.

Feeling or being sick

Feeling or being sick is usually well controlled with anti sickness medicines. It might help to avoid fatty or fried foods, eat small meals and snacks and take regular sips of water. Relaxation techniques might also help.

It is important to take anti sickness medicines as prescribed even if you don’t feel sick. It is easier to prevent sickness rather than treat it once it has started.

Inflammation at the site of injection

You might have some inflammation at the site of infection. This can cause swelling, redness and discomfort. Tell your healthcare team if this happens. 


Tell your doctor or nurse if you have headaches. They can look into what is causing them and give you medicine to help.

Back pain

You might have back pain. Speak to your doctor if this is a problem for you. They can prescribe medicine to help.

Difficulty swallowing

Let your healthcare team know straight away if you have any problems swallowing.

Rare side effects

These side effects happen in fewer than 1 in 100 people (fewer than 1%). You might have one or more of them. They include:

  • whole body infection (sepsis) causing fever, being sick, confusion, dizziness and chills
  • brown or black spots on the skin (lentigo)
  • numbness, weakness or pain in lower arms or legs or pins and needles in your hands and feet
  • loss of ability to move (paralysis of) legs and lower body
  • inflammation of the sac surrounding the heart
  • shortness of breath
  • pain, burning, reddening and blistering of the palms of the hands and soles of the feet
  • muscle and joint pain

Other side effects

If you have side effects that aren’t listed on this page, you can look at the cytarabine into the bloodstream page.

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do I need to know?

Other medicines, foods and drinks

Cancer drugs can interact with medicines, herbal products, and some food and drinks. We are unable to list all the possible interactions that may happen. An example is grapefruit or grapefruit juice which can increase the side effects of certain drugs.

Tell your healthcare team about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies. Also let them know about any other medical conditions or allergies you may have.

Loss of fertility

You may not be able to become pregnant or get someone pregnant after treatment with this drug. Talk to your doctor before starting treatment if you think you may want to have a baby in the future.

Men might be able to store sperm before starting treatment. And women might be able to store eggs or ovarian tissue. But these services are not available in every hospital, so you would need to ask your doctor about this.    

Contraception and pregnancy

This treatment may harm a baby developing in the womb. It is important not to become pregnant or get someone pregnant while you're having treatment and for at least 6 months afterwards.

Talk to your doctor or nurse about effective contraception before starting treatment. Let them know straight away if you or your partner become pregnant while having treatment. 


It is not known whether this drug comes through into the breast milk. Doctors usually advise that you don’t breastfeed during this treatment.

Treatment for other conditions

If you are having tests or treatment for anything else, always mention your cancer treatment. For example, if you are visiting your dentist.


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 one of the shingles vaccines called Zostavax.

You can have:

  • other vaccines, but they might not give you as much protection as usual
  • the flu vaccine (as an injection)
  • the coronavirus (COVID-19) vaccine - talk to your doctor or pharmacist about the best time to have it in relation to your cancer treatment

Members of your household who are aged 5 years or over are also able to have the COVID-19 vaccine. This is to help lower your risk of getting COVID-19 while having cancer treatment and until your immune system Open a glossary item recovers from treatment.

Contact with others who have had immunisations - You can 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 the oral typhoid vaccine. Sometimes people who have had the live shingles vaccine can get a shingles type rash. If this happens they should keep the area covered.

If your immune system is severely weakened, you should avoid contact with children who have had the flu vaccine as a nasal spray as this is a live vaccine. This is for 2 weeks following their vaccination.

Babies have the live rotavirus vaccine. The virus is in the baby’s poo for about 2 weeks and could make you ill if your immunity is low. Get someone else to change their nappies during this time if you can. If this isn't possible, wash your hands well after changing their nappy.

More information about this treatment

For further information about this treatment and possible side effects go to the electronic Medicines Compendium (eMC) website. You can find the patient information leaflet on this website.

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

Related links