Shareholder lawsuits alleging Merck concealed the health risks of its arthritis painkiller Vioxx (rofecoxib) have been revived by a US court.

The former blockbuster Vioxx, which at its height earned the company revenues of $2.5 billion a year, was withdrawn from the market in 2004 following evidence of a high risk of heart attack, stroke and death among users. The shareholders' group claims Merck directors covered up these risks.

The three-judge panel of the 3rd Circuit Court of Appeals ruled that the lawsuits should be sent back to the New Jersey federal judge who dismissed them in May 2006, saying that US District Judge Stanley R Chesler should have allowed the plaintiffs to amend their original complaint with additional materials.

Will new information affect lawsuit's merit?

The panel said the district judge needs to determine whether the additional materials would affect the lawsuit's merit. Since it is a shareholder suit, the plaintiffs would normally have been required to first make a demand on the company’s board of directors. But the plaintiffs said such a demand would have been futile at the time they began the lawsuit. “Of course, we express no opinion about whether the newly acquired facts that are included in the amended complaint will alter this analysis," the 3rd Circuit judges wrote.

Legal representative for Merck, Ted Mayer, said: “We look forward to presenting our arguments anew to the district court”. Meanwhile, the lawyer for the plaintiffs, Darren Roberts, said the decision to go back to court was “a tremendous victory for Merck shareholders”.

Merck is facing more than 27,000 product liability lawsuits related to Vioxx after a study found it doubled the risk of heart attack and stroke in patients who used it for at least 18 months.