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Trade/other name(s): Oncospar, PEG-L-asparaginase

Why would this drug be used?

Pegaspargase is used along with other drugs to treat acute lymphocytic leukemia. It is often used if the patient is allergic to L-asparaginase.

How does this drug work?

Pegaspargase is an enzyme type of anti-cancer drug (anti-neoplastic). It gets rid of asparagine, which is a substance cells need to grow. Normal cells can make their own asparagine, but some leukemia cells cannot. This interferes mainly with the growth of leukemia cells, though some normal cells are affected.

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), gout, infections, or if you have had kidney stones. These conditions may require that your medicine dose, regimen, or timing be changed.
  • If you have diabetes. Pegaspargase can cause diabetes, and may worsen existing diabetes.
  • If you have ever had pancreatitis (an inflamed pancreas). Pegaspargase can cause severe pancreatitis with bleeding, and the risk is higher if you have had it before.
  • If you have ever taken asparaginase and had serious blood clots, pancreatitis, allergic reaction, or bleeding. These may happen again with pegaspargase
  • 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. This drug can lower sperm count and interfere with the menstrual cycle. Although sterility has not been reported with pegaspargase, some chemotherapy 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

Pegaspargase affects the way methotrexate works. Whether it hinders or helps depends on when it’s given: with, before, or after the methotrexate. Together they may increase the risk of liver damage. Other chemotherapy drugs may also be affected by pegaspargase.

Any drugs or supplements that interfere with blood clotting can raise the risk of bleeding during treatment with pegaspargase. 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?

Pegaspargase is given as shots into the muscle, or it can be infused into the vein over 1 to 2 hours. The dose depends on your size and treatment plan. The doctor will usually keep you for an hour after the medicine is given to be sure that any reaction you may have can be treated. Pegaspargase is generally given no more often than every 2 weeks.


This drug can cause allergic reactions. Tell your nurse or doctor right away if you notice feeling short of breath, swelling in your mouth or throat, lightheaded or dizzy (due to low blood pressure), itching, hives (welts on the skin), rapid heartbeat, or any sensation that is different while you are getting this medicine and for a few hours afterward.

This drug may increase your risk of blood clots. Call your doctor if you notice severe headache, swelling in an arm or leg, shortness of breath, chest pain, weakness, or seizures.

This drug may rarely lower your blood clotting factors during treatment, which can increase your risk of bleeding. Talk 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), vitamin E, or non-steroidal anti-inflammatory drugs such as ibuprofen. Tell your doctor right away if you have unusual bleeding such as nosebleeds, bleeding gums when you brush your teeth, or black, tarry stools. Avoid contact sports or situations where head injury is possible.

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° F or higher), shaking chills, pain when passing urine, a new cough, or bringing up sputum.

Do not get any immunizations (vaccines), either during or after treatment with this drug, without your doctor's OK. Pegaspargase 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.

This drug can cause problems with increased blood sugar. This can cause symptoms like increased thirst, increased hunger, and increased urine output. Call your doctor or nurse right away if you notice these symptoms.

Call your doctor or nurse if you have pain in the upper abdomen (above the belly button), especially if you have nausea and vomiting as well. These may be symptoms of pancreatitis, which can be dangerous and must be treated.

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

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.


  • Nausea
  • Vomiting
  • Diarrhea
  • Loss of appetite
  • Tiredness (fatigue)
  • Drowsiness
  • Depression
  • Abnormal blood tests which suggest that the drug is affecting the liver (Your doctor will discuss the importance of this finding, if any.)*

Less common

  • High blood sugar, which usually goes away when the drug is stopped*
  • Mild anemia, which can cause tiredness or fatigue
  • Allergic reaction*


  • Inflammation of the pancreas, with abdominal pain and vomiting*
  • Low white blood cell count with increased risk of infection*
  • Low platelet count with increased risk of bleeding
  • Low levels of clotting factors (made by the liver) with increased risk of bleeding*
  • Abnormal blood tests which suggest that the drug is affecting the kidneys (your doctor will discuss the importance of this finding, if any.)
  • Numbness or tingling of the fingers
  • Confusion
  • Blood clots, which can affect the brain, lungs, or other parts of the body*
  • Death due to pancreatitis or other cause

*see the “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 in 1994

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: 06/18/2014
Last Revised: 06/18/2014