Does Ondansetron (Zofran) Cause Birth Defects?

April 24, 2015 — San Diego, CA

When Zofran flashed across the television as causing birth defects I was alarmed. A friend of mine’s baby was born with a Tracheal Esophageal Fistula. Knowing she relied heavily upon the prescribed medication Ondansetron during her first trimester I immediately began research into the drug poring over scientific journals to get an accredited answer to my questions. What the research revealed is a must for any pregnant or nursing mother prescribed it by their doctors.

To understand Ondansetron requires research, not on any .com or opinion site but accredited journals so I began with a paper from the Journal Reproductive Toxicology for a simple answer to a complex question.

Ondansetron, non-generic Zofran, is an antiemetic. Antiemetics are a complex name for medications used to treat nausea and vomiting. Ondansetron is specifically approved for the treatment of nausea and vomiting in patients following chemotherapy, irradiation, and surgery. The medication’s usage is never labeled as a medication to treat nausea and vomiting (NVP) in pregnant woman. Sometime in the 90s, despite it not being intended for such a use, doctors began prescribing it for NVP in pregnancy. Once the prescription Zofran became generic, Ondansetron, its use exploded to the point where over one million woman are now taking the drug for NVP. The point repeated over and over is Ondansetron is not labeled for this. I read and reread the company’s included prescribing information which clearly states the drug to be used for prevention of nausea and vomiting in chemotherapy, irradiation, and surgery situations not as a casual choice for NVP.

I wondered if perhaps the pharmacy label might give a different impression. The label does state a doctor may prescribe this medication for other conditions which is nothing new. However, it does not state it’s approved for treatment of NVP and says the doctor should discuss with those who are pregnant whether the benefits outweigh the risks. The articles go further to state the FDA has not approved nor advises the use of Ondansetron in NVP. Why would they? The prescribing information itself makes that clear.

All of this information was excellent but didn’t answer the question of whether Ondansetron (Zofran) causes birth defects. I needed to dive in deeper into the literature. The early studies on Ondansetron had small sample sizes and little data to go on. Researchers tentatively said there was no evidence of Ondansetron causing harm to a fetus but followed it up by stating there was not enough research to reach a clear conclusion. None of them recommended the drug as being the first choice for NVP.

Only within the last year or two have studies been able to make clear the potential for birth defects related to Ondansetron. This is partly due to the huge increase in woman now taking the drug for NVP. One of the most important studies compared the use of Ondansetron for NVP with drugs specifically developed for the condition.

The link between Ondansetron increasing the risk of babies born with a cleft palate/lip, like the lawsuit commercials said, was supported by some studies while others argued against such congenital malformations. What the information did reveal was an increase in the risk of cardiovascular malformations in woman who had taken the medication. In other words, taking Ondansetron means your baby is at a higher risk for being born with certain heart issues, one of the most common being a septum defect.

Ondansetron is from a class of medications which have the potential to cause  Long QT Syndrome and cardiac arrhythmia. In the simplest words, they can affect the heart’s normal rhythm. This potential complication is listed everywhere from the prescribing information to the pharmacy label. It’s not a secret. Just like seizure medications have the potential side effect of developing Steven Johnson’s syndrome. Whether it be herbal or pharmaceutical there is always a risk to our bodies for a negative response.

When you are pregnant your heart is beating both for you and your unborn baby. If the heart’s normal rhythm is disrupted the effects on a still-developing fetus is more likely than the adult heart to be negatively affected. Disruption of the rhythm can impede blow flow even oxygen to the baby’s brain. Imagine what just a few moments have the potential to do during a crucial time in development.

The Journal of Obstetrics and Gynecology has raised the question as to why this drug is being prescribed at all in pregnancy. Ondansetron’s intended usage is not for NVP, the FDA has not approved it for use in pregnancy. All a doctor needs to do is a quick search of the literature, read the prescribing information, even do a two minute google search and they would see the red flag. Here’s a direct quote from Ondansetron’s prescribing information:

Pregnancy Teratogenic Effects: […] this drug should only be used during pregnancy if clearly needed. 

This goes not only for pregnant woman but for nursing mothers as well. Ondansetron’s warning label clearly states:
Nursing Mothers: Ondansetron is excreted in the breast milk of rats. It is not known whether Ondansetron is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Ondansetron is administered to nursing mothers.

 Why any doctor would immediately choose Ondansetron without first outweighing its risks and benefits is downright crazy. The saddest part is there are other well-studied medications which are specifically approved for NVP in pregnancy. One study even compared two of them to Ondansetron. No surprise. Ondansetron, the one medication whose use is not for NVP, was the only one who showed a significant risk for cardiovascular malformations.

The research has left me wondering where our doctors have gone wrong.  Ondansetron is not an evil drug; in fact, it has been a life-changer for those who it is intended for. Those wanting to claim the drug company as responsible need to be reminded this medication is approved for the use in nausea and vomiting for patients chemotherapy, irradiation, and surgery NOT NVP. The FDA has not approved Ondansetron for NVP and medical journals have made it clear Ondansetron should not be prescribed without first exhausting safer options.

At the end of my research I am confident my friend’s baby (who is a healthy beautiful two year-old today) was not affected by her use of Ondansetron in pregnancy. If his Tracheal Esophageal Fistula had been accompanied by heart defects (thank goodness he had none) I would be asking a lot more questions .Questions I encourage any pregnant or nursing mother prescribed to ask their doctor. You have a right to know why your doctor is prescribing Ondansetron without first speaking to you about the risks versus benefits. Hearing a doctor say ‘I don’t know’ is no excuse. Babies deserve phenomenal care so make sure yours has the best.

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