Merck & Co is facing another setback in its legal battle to prove that it did not mislead the public over the safety of its withdrawn painkiller Vioxx, after plaintiffs in the ongoing federal lawsuit filed for a mistrial.

The filing comes in the wake of allegations by the editors of the New England Journal of Medicine that Merck deliberately excluded three cases of heart attack and other relevant data when it published the findings of the VIGOR trial in 2000.

According to a report in the Wall Street Journal, Judge Eldon Fallon is taking the mistrial filing under consideration, but would still prefer to hear the jury’s decision. The jury started deliberating over the case last Thursday, but has yet to reach a verdict, saying on Saturday it was unable to reach a unanimous position. Deliberations will resume later today.

The lawsuit has been brought by the widow of Richard Irvin, a 53-year-old man who died of a heart attack after taking Vioxx (rofecoxib) for about a month to relieve back pain. Her lawyers maintain that Vioxx is the cause of his heart attack, but Merck insists that underlying heart disease was to blame. All the evidence, it maintains, suggests that long-term exposure to Vioxx of 18 months or more is needed to increase the risk of heart attack.

Irvin’s short treatment period was expected to make the case an easy win for Merck, but the NEJM’s pronouncements have thrown a spanner into the drugmaker’s defense, boosting claims that the company deliberately disguised the pain reliever's risks. Merck has always claimed it made the link public as soon as the evidence became available.