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Trade/other name(s): Ara-C, Cytosar-U, cytosine arabinoside

Why would this drug be used?

Cytarabine is used to treat certain types of leukemias. It may also be used for non-Hodgkin lymphoma.

How does this drug work?

Cytarabine belongs to the group of drugs called anti-metabolites. It keeps cells from making DNA and RNA, which stops the growth of cancer cells.

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, or foods.
  • If you have any medical conditions such as kidney disease, liver disease (including hepatitis), heart disease, congestive heart failure, diabetes, gout, or infections. These conditions may require that your medicine dose, regimen, or timing be changed.
  • If you have had kidney stones. Your doctor may give you extra fluids to prevent recurrence.
  • If you have ever been treated with L-asparaginase, a type of chemotherapy. You may have a higher risk of pancreatitis (inflamed pancreas) when getting cytarabine.
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. This drug may cause birth defects if either the male or female is taking it at the time of conception or during pregnancy. Check with your doctor about what kinds of birth control can be used with this medicine.
  • If you are breast-feeding. It is not known whether this drug passes into breast milk. If it does, it could harm the baby.
  • If you think you might want to have children in the future. Some drugs can cause sterility. Talk with your doctor about the possible risk with this drug and the options that may preserve your ability to have children.
  • About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

Talk with your doctor if you are taking digoxin (a heart medicine). You may need special testing to be sure that your digoxin level stays in the desired range.

Certain antibiotics do not work well with cytarabine and may need to be changed.

Any drugs or supplements that interfere with blood clotting can raise the risk of bleeding during treatment with cytarabine. These include:

  • vitamin E
  • non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen (Advil, Motrin), naproxen (Aleve, Naprosyn), and many others
  • warfarin (Coumadin)
  • ticlopidine (Ticlid)
  • clopidogrel (Plavix)

Note that many cold, flu, fever, and headache remedies contain aspirin or ibuprofen. Ask your pharmacist if you aren't sure what's in the medicines you take.

Check with your doctor, nurse, or pharmacist about other medicines, vitamins, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Cytarabine or cytosine arabinoside is given by infusion in a vein over 20 minutes to 2 hours, or as a continuous infusion over 24 hours. It can also be given as a shot under the skin or into the space around the spinal cord. The dose, how long the treatment lasts, and how often the medicine is given, depends on your size and your type of cancer.

If your doctor prescribes the shot under the skin, you or a family member can be taught to give it at home. Make sure to keep the medicine in its original container in a safe place in the refrigerator, and the shot equipment out of the reach of children and pets. Store the used needles in a closed needle bucket and return them to your doctor or nurse.


You may have nausea and vomiting on the day you receive this drug or in the first few days afterward. Some people also have abdominal pain with this. Your doctor may give you medicine before your treatment to help prevent nausea and vomiting. You will likely also get a prescription for an anti-nausea medicine that you can take at home. It is important to have these medicines on hand and to take them as prescribed by your doctor.

Some people have fever, body aches, rash, red eyes, and feel very tired about 6 to 12 hours after getting cytarabine. This is known as cytarabine syndrome. Call the doctor if the fever persists, or if you notice pain in your chest, trouble breathing, or other serious symptoms.

Your doctor will likely test your blood throughout your treatment, looking for possible effects of the drug on blood counts (described below) or on the liver, kidneys, or other body organs. Based on the test results, you may be given medicines to help treat any effects. Your doctor may also need to reduce or delay your next dose of this drug, or even stop it altogether. Be sure to keep all your appointments for lab tests and doctor visits.

This drug can lower your white blood cell count, especially in the weeks after the drug is given. This can increase your chance of getting an infection. Be sure to let your doctor or nurse know right away if you have any signs of infection, such as fever (100.5°or higher), chills, pain when passing urine, a new cough, or bringing up sputum.

This drug may lower your platelet count in the weeks after it is given, which can increase your risk of bleeding. Speak with your doctor before taking any drugs or supplements that might affect your body's ability to stop bleeding, such as aspirin or aspirin-containing medicines, warfarin (Coumadin), or vitamin E. Tell your doctor right away if you have unusual bruising, or bleeding such as nosebleeds, bleeding gums when you brush your teeth, or black, tarry stools.

This drug may lower your red blood cell count. If this occurs, it is usually a few weeks after starting treatment. A low red blood cell count (known as anemia) can cause shortness of breath, or make you to feel weak or tired all the time. Your doctor may give you medicines to help prevent or treat this condition, or you may need to get blood transfusions.

This drug can cause the rapid killing of tumor cells, which in some cases has led to serious kidney damage within the first 24 hours of treatment (a condition known as tumor lysis syndrome). This is more likely if you have a very large number of cancer cells in the body. If your doctor feels you might be at risk, he or she will give you medicines and/or fluids to help prevent this.

This drug may cause sores in the mouth or on the lips, which often occur within the first few weeks after starting treatment. This can cause mouth pain, bleeding, or even trouble eating. Your doctor or nurse can suggest ways to reduce this, such as changing the way you eat or how you brush your teeth. If needed, your doctor can prescribe medicine to help with the pain.

Do not get any immunizations (vaccines), either during or after treatment with this drug, without your doctor's OK. Cytarabine may affect your immune system. This could make vaccinations ineffective, or could even lead to serious infections if you get a live virus vaccine during or soon after treatment. Try to avoid contact with people who have recently received a live virus vaccine, such as the oral polio vaccine or smallpox vaccine. Check with your doctor about this.

Avoid pregnancy during and for at least a few months after treatment, since exposure to the drug can harm the fetus. Talk with your doctor about this.

Note that higher doses of this drug (mostly in experimental studies) have led to heart damage, trouble walking and talking, confusion, seizures, severe lung damage and more. The side effects and precautions listed here are for standard doses of the drug.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.


  • low white blood cell count with increased risk of infection*
  • low platelet count with increased risk of bleeding*
  • low red blood cell count (anemia) with symptoms like weakness, tiredness, shortness of breath*
  • nausea*
  • vomiting*
  • stomach pain*
  • tiredness (fatigue)
  • sores in mouth or on lips*

Less common

  • diarrhea
  • loss of appetite
  • rash*
  • hair loss or thinning (may include face and body hair)
  • fever*
  • muscle and bone aches*
  • liver damage
  • blood clots and inflammation of the vein where the drug was given


  • red or swollen eyes*
  • sleepiness
  • muscle weakness
  • trouble walking
  • trouble writing
  • slurred speech
  • kidney damage
  • fetal changes that may lead to birth defects, prematurity, or serious illness in the newborn if you become pregnant while taking this drug
  • allergic reaction with itching, dizziness, trouble breathing, or swelling of the face, mouth, or throat
  • death due to infection, bleeding, or other causes

*See "Precautions" section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved before 1984 (FDA cannot verify dates of drugs approved before 1984).

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 02/01/2010
Last Revised: 02/01/2010