Zofran (ondansetron), manufactured by GlaxoSmithKline (GSK), is a member of a class of drugs known as 5-HT3 receptor antagonists, which work by blocking the actions of serotonin. Zofran was approved by the Food and Drug Administration (FDA) in January 1991, to treat chemotherapy-related nausea, and the approval was later expanded to treat postoperative nausea and vomiting. Since then, it has been increasingly prescribed for off-label uses, such as use by pregnant women suffering from morning sickness. Studies show that Zofran use by pregnant women can lead to a heightened risk of severe birth defects, including heart development irregularities, cleft lip and cleft palate.

In 2012, GSK agreed to pay the United States Department of Justice $3 billion to settle numerous civil and criminal allegations, including the illegal marketing of Zofran. The company is now facing lawsuits filed on behalf of children born with heart defects or craniofacial birth defects because their mothers took Zofran during pregnancy.