An official GlaxoSmithKline (GSK) memo has revealed that scientists deliberately withheld information linking the company’s blockbuster antidepressant Paxil to heart-related birth defects.

The memo was revealed at a trial in Philadelphia, US, which is examining more than 600 cases alleging that the company knew Paxil caused birth defects but hid the information to boost profits.

The drug, which was approved for US use in 1992, generated about $942m in sales for the company in 2008, accounting for 2.1% of GSKs total revenue.

According to available information, GSK failed to take into account Danish animal studies that showed that young rats died after taking low doses of the drug.

The company continued to deny that Paxil increased the risk of birth defects up until 2003, when the US Food and Drug Administration ordered Glaxo and other makers of antidepressants to carry out more stringent safety studies.

In 2004, the drugmaker agreed to pay the state of New York $2.5m to resolve claims that officials suppressed research showing Paxil may increase suicide risk in young people.