Strong Pregnancy Warnings on Canadian Zofran Label

April 16, 2015 — Three years after the Justice Department accused GlaxoSmithKline (GSK) of illegally marketing the anti-nausea drug Zofran to pregnant women, the label in the United States still has less prominent warnings about fetal risks compared to the label in Canada.

GSK is accused of failing to state prominently on the label that there is little evidence Zofran is safe for the treatment of morning sickness during pregnancy. About 1 million pregnant women use Zofran “off-label” every year.

Lawsuits claim GSK failed to update the label, despite knowing that the safety of Zofran for pregnant women had not been established. Furthermore, hundreds of women had reported birth defects after taking Zofran and several epidemiological studies reported an increased risk of birth defects.

Despite growing concern, the label on Zofran has carried the following pregnancy warnings since 1993:

“Pregnancy: Teratogenic Effects: Pregnancy Category B. Reproduction studies have been performed in pregnant rats and rabbits at I.V. doses up to 4 mg/kg per day and have revealed no evidence of impaired fertility or harm to the fetus due to ondansetron. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.”

By contrast, the Product Monograph for Zofran in Canada clearly states that “the safety of ondansetron for use in human pregnancy has not been established,” and “the use of ondansetron in pregnancy is not recommended.”

Research based on an extensive database of births in Denmark from 1997-2010, encompassing 900,000 births, found evidence that Zofran doubled the risk of having a baby with a heart defect, leading to a 30% increased risk of birth defects overall. About 4.7% of babies exposed to Zofran had a birth defect, compared to 3.5% of non-exposed babies in the study.