Evidence Linking Zofran and Birth Defects Growing for Years

March 23, 2015 — Studies linking Zofran and a potential risk of birth defects has been growing for years, which adds evidence to lawsuits alleging that GlaxoSmithKline (GSK) knew or should have known about the risk.

Zofran (ondansetron) is only approved for the prevention of chemotherapy-induced nausea and vomiting. Every year, about 1 million pregnant women use it “off-label” for the treatment of morning sickness in the first trimester.

Although many doctors assume Zofran is safe, a growing number of studies have highlighted birth defect concerns when it is used in early pregnancy.

In the 1980s, animal studies indicated that Zofran could lead to intrauterine deaths and malformations. GSK has never tested Zofran in pregnant women, but the animal studies proved that Zofran could cross the placenta and potentially influence fetal development.

In 2006, researchers in Hong Kong concluded that Zofran could cross the human placenta in significant levels. Other studies have shown that it stays active in the fetus longer than it does in a pregnant woman.

In November 2011, a study published in Birth Defects Research found a 2.4-fold increased risk of cleft palate in babies exposed to Zofran.

Several other studies have found that Zofran doubles the risk of heart defects, especially “hole in the heart” defects, and increases the risk of birth defects overall by 30%.

Lawsuits now accuse GSK of putting corporate profits above public safety by marketing Zofran to pregnant women without warning about birth defects. In 2012, GSK paid a $3 billion settlement with the Justice Department for illegally marketing several drugs, including Zofran in pregnant women.