GlaxoSmithKline P.L.C. must pay $2.5 million to settle a claim that its antidepressant Paxil caused severe heart defects in a 3-year-old Bensalem boy, a Philadelphia Common Pleas Court jury found today.

The verdict is the first in 600 cases alleging that Glaxo knew Paxil caused birth defects and hid those risks to boost profit.

The drug, approved for U.S. use in 1992, generated about $942 million in sales last year, 2.1 percent of Glaxo's total revenue.

Glaxo, based in London, has major operations in the Philadelphia region.

Michelle David had claimed that her 3-year-old son, Lyam Kilker, suffered life-threatening heart defects because she had taken Paxil while pregnant with him.

The jury deliberated for just seven hours over two days, so when the verdict came back, David and her attorneys had braced themselves for a loss.

"We were just hoping and praying that the jury saw what we knew to be true," David said today, shortly after the award was announced.

David, 28, said she remained confident in her case because she came from a large family with no previous incidents of heart problems in babies.

"I just kept thinking, 'What did I do differently in my pregnancy,' " she said.

Glaxo issued a statement saying it disagreed with the verdict and would appeal.

"While we sympathize with Lyam Kilker and his family, the scientific evidence does not establish that exposure to Paxil during pregnancy caused his condition. Very unfortunately, birth defects occur in 3 to 5 percent of all live births, whether or not the mother was taking medication during pregnancy," the company's statement said.

The verdict arrives as the medical community is reassessing how to treat depression in pregnant women. An August report from the American Psychiatric Association and American College of Obstetricians and Gynecologists said depressed pregnant women should consider psychotherapy before taking antidepressants.

The report also said that women with moderate to severe symptoms should remain on their medications while pregnant, and that the medication decision was especially challenging for expectant mothers with milder depression because the risks might outweigh the benefits.

Depressed pregnant women may not take care of themselves well, which can affect the health of their babies. But the most popular type of antidepressant, selective serotonin reuptake inhibitors, or SSRIs, have been linked to various problems, including a higher incidence of pulmonary hypertension, a type of increased lung pressure that can lead to heart failure.

David and Lyam's attorneys, Sean Tracey of Houston and Jamie Sheller of the Philadelphia firm Sheller P.C., argued that Glaxo had withheld information from consumers and regulators about the risk of birth defects and had failed to properly test Paxil.

"I was very happy" with the verdict, Tracey said.

By a 10-2 margin, jurors said Glaxo officials had "negligently failed to warn" the doctor treating David about Paxil's risks and concluded the medicine was a "factual cause" of the child's heart defects.

But the jury also found that Glaxo's handling of the drug was not "outrageous," meaning the family could not seek punitive damages against the drugmaker.

Jurors awarded the family more than double the $1.2 million they had sought for Lyam's past and future medical care and other damages caused by the heart defects.

David said the money would help pay for Lyam's future health care and other needs.

In its statement today, Glaxo said it had "acted properly and responsibly in conducting its clinical trial program for Paxil, including sharing documentation and submitting results from studies on Paxil to regulators."

Lyam was hospitalized for several months after his birth so doctors could repair his heart. He will require more surgeries as he grows.

David is a former cheerleader for the Philadelphia 76ers.

The case was heard by Judge Stephen Levin in Common Pleas Court.

The U.S. Food and Drug Administration initially classified Paxil as a drug with no known connections to birth defects. In 2005, the agency reclassified it as a drug with some evidence of human fetal risk, but it allowed doctors to continue prescribing it to women of childbearing age if the benefits outweighed the risks.

The reclassification means Paxil is considered more risky during pregnancy than other SSRIs, including Pfizer Inc.'s Zoloft and Eli Lilly & Co.'s Prozac, which also are sold in generic versions.

Contact staff writer Miriam Hill at 215-854-5520 or hillmb@phillynews.com.

This article contains information from Bloomberg News.