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Antithymocyte Globulin


Brand names:

Atgam®, Thymoglobulin®

Other names:

ATG, ATGAM (horse, equine), or Thymoglobulin (rabbit)

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What is antithymocyte globulin (ATG)?

Antithymocyte globulin (ATG) is a medicine that suppresses the immune system (immunosuppressant). It is used to decrease the body’s natural immune system response and prevent or treat GVHD after stem cell transplant. It may also be used to prevent rejection of organ transplants or to treat aplastic anemia.

The medicine is made of proteins taken from the blood of either rabbits or horses. The type of ATG used will depend on the condition being treated.

This medicine is a clear liquid given into a vein by IV infusion. The infusion usually lasts at least 4 hours and may take up to 24 hours. The infusion may be slowed down to lessen side effects.

To lower the chance of allergic reaction, your child will get medicine called pre-medications before the infusion starts. Your child may also get a small test dose before starting the medicine to see if they will develop an allergic reaction.

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Given into a vein by IV

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Possible side effects

  • Infusion related reaction: Symptoms of an infusion reaction may include changes in blood pressure, difficulty breathing, fever, chills, nausea, and vomiting.
  • Feeling tired or weak
  • Headache
  • Fever and chills
  • Irritation at the IV site
  • Increased risk of infection
  • Muscle and joint pain, nausea and vomiting, or skin rash. This is often called “serum sickness” which can last for up to a couple weeks after the infusion.
  • Low blood counts
  • Skin rash
  • Skin sensitivity, sunburn

Symptoms of an allergic reaction may include rash, hives, itching, runny nose, fever, chills, headache, muscle ache, shortness of breath, coughing, tightness in the throat, dizziness, low blood pressure, pain in the chest, side, or back, and swelling of the face or neck.

Not all patients who get ATG will have these side effects. Common side effects are in bold, but there may be others. Please report any symptoms or side effects to your health care provider or pharmacist.

Find more information on side effects.

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Tips for patients and families

Be sure to discuss all questions and instructions with your care team or pharmacist.

  • Some patients may have a reaction to this medicine. Let your care team know about any symptoms during the infusion.
  • This medicine can weaken the immune system and increase the risk of infection. Wash hands often, keep patient areas clean, and avoid contact with people who are sick.
  • Talk to your care team before your child gets any immunizations. Vaccines may not be recommended for a period of time after getting this medicine.
  • Your child may bleed more easily, and wounds may heal more slowly. Brush teeth gently with a soft toothbrush, use an electric razor to shave, and avoid activities that can cause injury.
  • This medicine may make skin more sensitive to the sun and your child may sunburn easily. Take steps to protect skin from the sun. Have your child wear sunscreen and protective clothing. Avoid sun exposure when possible.
  • It is important that patients tell the care team if they are sexually active, pregnant, or breastfeeding.
  • Sexually active patients should take steps to prevent pregnancy during treatment and for 3 months after treatment is complete.