GlaxoSmithKline P.L.C. for years ignored evidence that its antidepressant Paxil may have caused birth defects, a lawyer told a Philadelphia jury today on behalf of a woman who says that taking the drug during her pregnancy caused her three year-old son's heart problems.

London-based Glaxo, which employs several thousand in the Philadelphia region, also told its scientists to avoid disclosing possible risks associated with the drug's use by pregnant women, said the lawyer, Sean Tracey.

"GSK said if there is any doubt, take it out," Tracey said, quoting from the company's core safety philosophy. "That's the exact opposite of what the regulations say, which is that if there is any evidence of association, you need to put it in."

Tracey represents Bucks County resident Michelle David, a former cheerleader for the Philadelphia 76ers, who is making the claim for her son, Lyam Kilker, who appeared briefly in the courtroom this morning.

GlaxoSmithKline's lawyer Chilton Varner said there is no evidence that Paxil caused Kilker's heart problems.

The case is being heard in Common Pleas Court.

Tracey walked jurors through a series of documents that he said showed that Glaxo knew before Paxil went on the market that rats administered the drug were more likely to have pups that didn't survive past four days and that the rate of death increased with higher doses of Paxil.

In the late 1980s, at about the same time as the rat study, an internal Glaxo scientist warned that "there remains the possibility that this compound could be teratogenic at higher dose levels." A teratogenic agent is one that can cause birth defects. Tracey said Glaxo had ignored links between Paxil and birth defects for 20 years.

The trial is the first of more than 600 cases alleging that Glaxo knew Paxil caused birth defects and hid those risks to pump up profits. Approved for U.S. use in 1992, the drug generated about $942 million in sales last year, 2.1 percent of Glaxo's total sales.

Glaxo lawyer Varner said the company carefully reviewed and reported any sign of problems to federal authorities. She accused Tracey of cherry-picking sentences from documents and predicted that when jurors see all the evidence, they will believe it will show that "Paxil has been tested in trials as much as any drug ever."

Since Paxil and similar drugs, including Prozac and Zoloft, have come on the market, the rate of heart birth defects has not changed, she said.

Varner also said that even though Kilker was hospitalized for five months after his birth and underwent surgeries to repair his heart, the boy today "is functioning just as a soon-to-be-4-year-old boy should. He has no cardiac symptoms, is on no cardiac medicines, has no residual defects, no illnesses or hospitalizations, no chest pain or palpitations, no leg pain or cramps, and no special needs. He is at preschool and runs and walks like a 4-year-old should."

Tracey said Kilker eventually will need another surgery. He also painted Glaxo as a company working hard to deny problems with one of its best-selling drugs. By 1997, the company received reports of 50 miscarriages or intrauterine deaths. When the company studied whether there was a connection between Paxil and birth defects, its scientists called the number of birth defects an "alarming finding." But those words were not included in the final version of the report, and Glaxo did not give the report to the FDA, even though it was required to do so.

Tracey said that in 2001, a woman wrote to Glaxo asking for more information on Paxil. The drug had alleviated her anxiety, but when she was six months pregnant, her doctor diagnosed birth defects and she aborted the fetus. In her letter, the woman asked Glaxo if it knew of any connections between Paxil and birth defects because she wanted to keep taking the drug but also wanted children.

A group of Glaxo scientists determined that the it was "almost certain" that Paxil had caused the birth defects but did not tell the woman or the FDA that, Tracey told the courtroom.

"What they did next was nothing. They didn't tell her. They didn't tell the FDA," he said.

The FDA initially classified Paxil as a Category B drug, meaning animal studies suggested no problem. It eventually changed to C and then D, meaning there is positive evidence of human fetal risk but allowing doctors to continue prescribing the drug to women of childbearing age if the benefits outweigh the risks.

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