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Popular Nausea Drug Zofran May Increase Risk of Birth Defects

Woman holding pregnant belly

A recent study casts doubt on the safety of Zofran, a popular morning sickness and nausea drug sometimes prescribed to pregnant women — and findings suggest the drug increases the risk of severe birth defects and injury to the mother.

Zofran is a 5-HT3 receptor antagonist manufactured by GlaxoSmithKline and is also available in its generic form, ondansetron. It works by affecting serotonin levels in the brain and was originally approved in 1991 to treat nausea and vomiting in cancer patients or after surgery. But, doctors continue to prescribe it “off-label” to treat nausea and vomiting during pregnancy (NVP).

Doctors also prescribe Zuplenz, a similar drug, to mothers suffering from morning sickness. With the equivalent chemical makeup as Zofran, this drug can engender pregnancy.

A study by Dr. Gideon Koren published in the December 2014 issue of American Journal of Obstetrics and Gynecology highlights the risks of pregnant women taking Zofran and conflicting studies that cannot rule out dangers to a fetus. Koren is affiliated with The Motherisk Program, The Hospital for Sick Children and the University of Toronto, Canada.

The study of 900,000 Danish women in August 2013 review found “2-fold increased risk of cardiac malformations with ondansetron (Zofran), leading to an overall 30 percent increased risk of major congenital malformations.”

Around 80 percent of pregnant women suffer from NVP, and about 1 million pregnant women are exposed to Zofran or its generic version every year, Koren reported.

The study also compared Zofran to metoclopramide, another drug used to treat NVP that was not associated with birth defects in the first trimester. Study authors say there are other safer FDA-approved treatments for NVP, such as doxylamine and pyridoxine.

“There is no reason for women to be exposed to a drug of unproven maternal and fetal safety” when there are safer options currently available, Koren wrote.

Conflicting Data

Earlier studies found no safety issues with Zofran, but newer research suggests the early data was not accurate enough to draw good conclusions.

For instance, an earlier and smaller study of 176 women found no connection between the drug and malformations, but the sample size was too small to detect any risk that was less than three-fold. So it could not actually rule out the possibility of risk.

In February 2013, scientists published in the New England Journal of Medicine a study of 2,000 women from a Danish birth registry spanning from 2004 to 2011. It revealed that the medication did not pose a harm to fetuses. However, half the women in the study began taking the drug at about 10 weeks – past the window of time when malformations could develop. Doctors felt the data was sound.

Several months later at a meeting of the International Society of Pharmacoepidemiology, Danish researchers presented their evidence collected from their 13 years of data. It remains the sample set published to date. This study found that 58 women out of 1,248 that took ondansetron in the first trimester had a baby with a birth defect, representing a 30 percent increased risk.

Glaxo Paid $3 Billion to Settle Fraud Allegations

A real side effect of Zofran’s questionable safety is lawsuits, both federal and civil. The Department of Justice sued GlaxoSmithKline for unlawful promotion and failure to report safety data of a number of its drugs, including Zofran. Glaxo did not admit that it illegally promoted the drug to treat morning sickness in pregnant women, but it did pay to settle civil allegations. The company agreed to pay $3 billion dollars in 2012 to resolve charges for Zofran and a number of other drugs.

Families of babies who suffered birth defect because of Zofran are also lining up to sue the drug giant because the drug’s label contains no safety warnings about birth defects. As of October 2015, these lawsuits were consolidated into a multidistrict legislation in the Massachusetts.

Women who used the drug during pregnancy gave birth to babies with birth defects, including cleft palates and lips, club feet, heart defects and craniosynostosis – a condition in which the skull is abnormally shaped and may not have enough space for the brain. This can cause vision problems, eating issues and mental impairment.

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