By Kayla Hyland, DVM; Rania Gollakner, BS, DVM, MPH

What is cytarabine?

Cytarabine (brand names: Cytosar-U®, DepoCyt®) is a systemic antineoplastic (anti-cancer) medication used primarily to treat blood cell cancers in dogs and cats. It has also been used to treat inflammation of the brain in dogs and cats.

Its use in cats and dogs to treat cancer or brain inflammation is “off label” or “extra label”. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions carefully, as their directions may be significantly different from those on the label.

How is cytarabine given?

Cytarabine is an injectable solution that is usually given intravenously by your veterinary professional in the hospital. It is sometimes injected under the skin. The beneficial effects may take a few days after administration, and the full effect may not be apparent for a few weeks.

Cytarabine is considered a hazardous drug. Do not handle if you are pregnant or nursing. Wear gloves when handling the waste, then seal the waste in a plastic bag before disposing in the regular trash. Because this medication is hazardous to other animals and people, all bodily waste such as urine, feces, and vomit should be disposed of with caution for a few days after your pet receives the medication. Pregnant women should not handle any waste from the pet.

Are there any potential side effects?

The most common side effects include gastrointestinal upset such as lack of appetite, nausea, vomiting, and diarrhea, as well as blood effects such as low red and white blood cell count, and low platelets. Other possible side effects include hair loss, mouth ulcers, neurological and liver disease, lethargy, and fever. Rarely, calcification at the injection site may occur if cytarabine is given under the skin.

The effects of this medication may last for a few days, and possibly longer in pets with liver or kidney disease. Therefore, although potential side effects may begin immediately, they may continue for several days after the medication is administered.

Are there any risk factors for this medication?

Cytarabine is toxic and must be used under very close supervision. It should not be given to pets that have a known allergic reaction. It should be given with caution to patients with liver, kidney, or bone marrow disease, or patients with infection. Use in pregnant or breeding animals is not recommended as it is possibly toxic to the fetus, and the risk versus the benefits must be considered. It is not recommended for use in nursing pets.

Are there any drug interactions I should be aware of?

Cytarabine should be used with caution when administered with flucytosine (5-FC), vaccines, or drugs that suppress blood cells, such as antineoplastics, immunosuppressants, or iron chelators.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Your veterinarian will monitor your pet with blood tests. Blood cell counts and liver and kidney function will be monitored to check for toxicities. Uric acid levels may also be monitored.

What should I do in case of emergency?

If diarrhea is severe or persists, contact your veterinarian. If bleeding, bruising, fever, shortness of breath, or severe lethargy occur, contact your veterinarian immediately. If they are not available, follow their directions in contacting an emergency facility.

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