The Effect of Azathioprine on a Developing Fetus

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What is Azathioprine?

Azathioprine, an anti-inflammatory agent is used for the treatment of rheumatoid arthritis and other inflammatory disease conditions. It suppresses the activity of the white blood cells and immune system chemicals that cause inflammation. It is readily used to minimize signs and symptoms of rheumatoid arthritis conditions such as swelling, pain, tiredness and morning stiffness besides others. Azathioprine is generally known by its brand name Imuran.

Azathioprine also acts as an immunosuppressive agent that reduces the immune systems capability of fighting infections. The drug was first developed for patients who received organ transplantation, for example, kidney transplantation. However, it was later used for the treatment of autoimmune diseases. Imuran is available in the form of 50 mg scored tablets. The doctor prescribes the dose depending upon the patient’s weight. Though the drug is beneficial for different diseases, it also causes various side effects such as leukopenia, nausea or vomiting, and infections. In addition, there are uncommon side effects like hair loss, diarrhea and joint pain among others. It is therefore, recommended that patients should notify to the healthcare provider if they experience any of the symptoms mentioned.

Azathioprine and Birth Defects

One of the major problems of azathioprine is that it causes birth defects in fetuses when the drug is taken by a pregnant woman. There are several strong indicators that exposure to this drug during pregnancy may have teratogenic effect on the fetus. A teratogen is a substance that causes birth defects. However, the severity of the defects will depend on the level of exposure and also the stage of pregnancy. Some of the symptoms of birth defects are mentioned below:

  • Flattened back of the skull

  • Heart defects

  • Extra digits

  • Retarded fetal growth

  • Pulmonary stenosis

  • Umbilical hernia

  • Lung anomalies

  • Hypospadias

Imuran and Breastfeeding

It has been found that if a woman is on medication then during breastfeeding, Imuran is passed through breast milk. Since there are various side effects in the infant, manufacturers recommend that women should not take this medicine when nursing. In case, a woman takes this medicine while breastfeeding, she needs to talk to the healthcare professional about the kind of risks associated with it.

According to the U.S. Food and Drug Administration (FDA), there is a specific category system that classifies the possible risks to a fetus when a certain kind of medicine is taken during pregnancy. This is called Category D. Imuran falls into this same category. The Category D medicines pose risks to the fetus, but, such medicines may be given to pregnant women if the healthcare provider believes that the benefits to the mother are greater than the possible risks to the unborn child.

Scientists used animal models such as pregnant rabbits and mice to find the possible risk of birth defects and they found that the drug increases the risks such as skeletal and organ problems on the fetus. And in humans, many infants were born with poorly functioning immune systems.

While the drug should be avoided for the treatment of rheumatoid arthritis during pregnancy whenever possible; there are situations when it is the best drug to help ensure the woman’s health, such as when Imuran is used to stop kidney transplant rejection.



(Web) Side Effects of Azathioprine –

(Web) Pregnancy-related conditions –