New York, NY - According to an internal company document, even as Merck & Co. was publicly playing down a study that highlighted the pain reliever Vioxx's potential heart attack risk, company researchers privately sought to reformulate Vioxx in 2000 to reduce its cardiovascular side effects.

A March 2000 study found that patients taking Vioxx were five times more likely to have heart attacks than individuals using the generic medicine naproxen. Merck, however, insisted at the time that this was a result of naproxen's cardioprotective properties and not any defect in Vioxx.

But behind the scenes, company scientists were considering combining Vioxx with another agent to reduce the risk of heart attacks and strokes, according to a document that was mistakenly provided by Merck to plaintiff lawyers as part of the evidence-gathering process in one of the hundreds of Vioxx lawsuits around the country.

The document, which was a communication between Merck researchers and the company's patent department, stated that the way Vioxx works to reduce pain might also increase cardiovascular problems. The scientists suggested a patent be sought for a combination drug mixing Vioxx with another agent to lessen the risk.

Thousands of wrongful death and injury lawsuits have been filed against Merck based on claims that the company hid Vioxx's risks since the company removed Vioxx from the market last September after a later study showed it doubled patients' risk of heart attacks and strokes. Analysts estimate the company's liability could reach as high as $18 billion.

The newly surfaced document is potentially among the most damaging to emerge since the drug's sales were suspended because it may call into question the defense that Merck officials were convinced of the drug's safety. "The document suggests a level of concern about the drug. The fact that they wanted to patent a different product raises questions--it says something," said Anthony Sebok, a professor at Brooklyn Law School.