UPDATED: FDA asks Pfizer for Zoloft label update highlighting birth defect risks

For years, Pfizer ($PFE) has shrugged off claims that its antidepressant Zoloft causes heart defects in newborns, fighting a raft of litigation alleging that the company did not adequately warn pregnant women taking the med about its potential risks. Now the FDA is weighing in on the issue, asking the company to acknowledge some studies that link Zoloft to heart defects in babies.

The agency wants Pfizer to change the med's label to reflect warnings from researchers who found "increased risk of congenital cardiac defects" in infants whose mothers took Zoloft, according to company court papers seen by Bloomberg. The FDA's request is part of a bigger initiative to reformat drug labels across the industry, Pfizer told the news outlet in an emailed statement. But the move also sheds new light on Zoloft's safety and potential risks.

Even though the majority of Zoloft studies turned up "no difference in major birth defect risk" for women taking the med, the drug's current label says there are "no adequate and well-controlled studies of pregnant women," according to filings seen by Bloomberg.

The FDA is staying mum on its request, saying "any conversations about labeling are confidential" and that the company would have to provide details, FDA spokeswoman Sandy Walsh told the news outlet in an email. And Pfizer is standing by its drug's safety, maintaining that Zoloft doesn't cause heart defects in babies and that its label warns women and their doctors about the med's risks.

"The label for the medicine has always accurately described both the benefits and risks of the medicine," the company told FiercePharma in an email. "Pfizer works closely with the FDA to monitor all relevant research, clinical and observational studies, post market reports, etc. to ensure all risks associated with Zoloft are understood, accurately communicated and studied as appropriate."

Pfizer has already chalked up some early courtroom wins for Zoloft. Earlier this year, juries in St. Louis and Philadelphia let the company off the hook in cases claiming that the med caused heart abnormalities in babies of women who took the drug while pregnant.

But Pfizer still faces hundreds of lawsuits alleging similar claims, not to mention reports that the company's own scientists warned its top executives about a possible link between Zoloft and birth defects. The FDA's latest move could add fuel to the legal fire, University of Michigan law professor Erik Gordon told the news outlet.

"Since the FDA is basically forcing them to acknowledge the existence of credible studies showing Zoloft may cause heart defects, a jury could conclude they were ignoring or hiding those links to sell more of their product," Gordon said, as quoted by Bloomberg.

But another legal expert actually sees Pfizer benefitting from the FDA request. The agency's request "puts a fence around the number of future cases that can be brought accusing Pfizer of failing to warn about heart defects," Carl Tobias, a product-liability law professor at the University of Richmond, tells Bloomberg. And it "gives the company some certainty about its overall exposure."

- read the Bloomberg story

Special Report: The top 15 pharma companies by 2014 revenue - Pfizer

Editor's Note: This story was updated with comments from Pfizer.

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