Pfizer is being “strongly urged” by the FDA to add more information to the label on its antidepressant medication Zoloft warning pregnant women taking the drug during the first trimester that it may lead to heart defects in their babies.

The agency asked Pfizer to change the warnings section of Zoloft’s prescribing information to indicate that some studies have shown an “increased risk of congenital cardiac defects in” newborns whose mothers took Zoloft during pregnancy, according to a court filing earlier this month.

Drug regulators have noted that most of the Zoloft research found no difference in birth defect risk for most users of the drug. The current labeling for Zoloft states there are “no adequate and well-controlled” studies of pregnant women.

The proposed new Zoloft label would state that the “weight of evidence” shows no difference in major birth defects between babies born to women who did not take Zoloft and those who did, but would also include the statement that “an increased risk of congenital cardiac defects, specifically septal defects…was observed in some published epidemiological studies” of pregnant women on Zoloft in the first trimester and list certain caveats about those studies’ limitations.

This request is reportedly a part of a larger FDA effort to make improvements to drug labels across the pharmaceutical industry.

Zoloft Overview

Zoloft has been widely prescribed to patients who suffer from symptoms of panic disorder and depression.  It was originally approved for use in the United States by the FDA in 1991.

Zoloft is a member of a class of drugs known as selective serotonin reuptake inhibitors, or SSRIs.  Zoloft was marketed as a safe medication as compared to other drugs that were on the market at the time of its approval.

That message proved to be effective as Zoloft eventually became one of the most prescribed medications in the United States.  At its height, tens of millions of prescriptions for Zoloft were written annually, generating more than $2.5 billion in revenue during 2006 alone.

Zoloft Birth Defect Lawsuits

Pfizer is currently facing a slew of lawsuits over Zoloft birth defects, consolidated in a multidistrict litigation (MDL) in federal court in Pennsylvania.

The Zoloft lawsuits totaled 545 as of July 2015 and include claims such as cardiac defects, spinal malformation, pulmonary hypertension, lung, abdominal and cranial defects, as well as septal defects.

The first bellwether trial is expected to begin in January 2016 and involves an Alabama mother, Deidra L. who alleges her son was born with congenital birth defects in 2008 as a result of taking Zoloft during pregnancy. Deidra claims her son has needed several surgeries to correct his Zoloft birth defects and will need continual care.

The outcomes of these early Zoloft bellwether trials will not be binding on other Zoloft lawsuits, but may help determine how the parties want to proceed.