Zofran Study Shows Morning Sickness Drug Can Cross Placenta

As concerns about the risk of birth defects from Zofran use during pregnancy continue to increase, new research suggests that the anti-nausea drug quickly crosses the placenta and stays in the bodies of newborns for an extended period of time. 

In a study published by the medical journal Clinical Pharmacology & Therapeutics, researchers from Stanford University, the University of Colorado, and the Royal Free Hospital in London examined plasma samples from 20 nonpregnant women and 40 pregnant women while investigating a possible treatment for neonatal abstinence syndrome.

While Zofran (ondansetron) is only approved for treatment of nausea and vomiting in chemotherapy or surgery patients, it is commonly used off-label as a morning sickness drug for pregnant women. It is also sometimes approved for prevention of neonatal abstinence syndrome, or withdrawal symptoms experienced by infants following exposure to illicit drugs before birth.

Researchers examined samples taken from umbilical cord blood, as well as from the infants after birth, in this new study. The findings suggest that Zofran use by pregnant women is characterized by rapid transplacental transfer and longer elimination half-life in neonates compared to their mother.

This is not the first study to find evidence that Zofran crosses the placenta when used by pregnant women, with researchers from Hong Kong raising concerns in a 2006 report published in the medical journal Clinical Pharmacokinetics. That observational study involved 41 women who requested surgical termination of pregnancy during the first trimester and were administered three doses of Zofran before the procedure. Zofran was found in all samples, with drug concentration in fetal tissue significantly higher than expected, leading researchers to call for further study at that time.

More recently, amid a number of reports involving children born with cleft palate, cleft lip, heart defects and other congenital malformations, several Zofran lawsuits have been filed on behalf of children, alleging that the manufacturer failed to adequately warn about the risks associated with use of the drug during pregnancy.

In 2012, a study found that women prescribed Zofran during the first trimester may be 2.37 times more likely to give birth to a child with a cleft palate.

In August 2013, a study was presented that found first-trimester of pregnancy Zofran use may double the risk of having a child with heart problems.

The complaints allege that GlaxoSmithKline failed to adequately study Zofran effects on the fetus or warn about the risks associated with use of the medication during pregnancy, which has never been determined by the FDA to be safe or effective.