Studies Find Zofran Crosses Placenta in Pregnancy

March 12, 2015 — In the last two decades, several studies have confirmed that Zofran crosses the placenta in significant amounts when it is used during pregnancy, which raises concern about a possible risk of birth defects for the fetus.

Lawsuits claim that the manufacturer of Zofran, GlaxoSmithKline (GSK), knew that Zofran could cross the placenta from animal studies conducted in the 1980s. These studies revealed evidence of intrauterine deaths, birth defects, and showed that the drug could cross the placenta of pregnant mammals.

Recent studies in humans have confirmed that Zofran readily crosses the placenta and exposes fetuses to the drug in substantial concentrations, but this information has not been disclosed to doctors who are prescribing Zofran for the “off-label” (unapproved) treatment of morning sickness.

One of the most recent studies confirming this risk was published in December 2014 by Clinical Pharmacology & Therapeutics.

Researchers warned that Zofran is characterized by “rapid transplacental transfer and longer elimination half-life in neonates compared to their mother,” meaning that the drug rapidly crosses the placenta and remains active in the fetus longer that it does in the mother. Conclusions were based on umbilical cord blood, as well as blood samples from newborns.

Another study, published in Clinical Pharmacokinetics in 2006, also concluded that a “significant amount” of Zofran crosses the placenta to a fetus. Conclusions were based on data from 41 pregnant women who requested surgical termination of pregnancy at the first trimester and were administered three doses of Zofran (8-mg) before surgery.