A federal jury in New Orleans awarded a retired F.B.I. agent $51 million for a mild heart attack that he suffered after taking the painkiller Vioxx for almost three years.

The verdict is the fourth multimillion-dollar loss for Merck, Vioxx's maker, in litigation over the drug. It came the day a state court judge in New Jersey overturned an earlier verdict in favour of the company in another Vioxx suit.

The company faces more than 14,000 lawsuits, covering almost 30,000 plaintiffs, from people who claim they or their relatives suffered heart attacks or strokes after taking Vioxx. The company says it did nothing wrong in researching or marketing the drug and plans to defend every lawsuit.

In the New Orleans case, a federal jury found unanimously that Merck had failed to warn doctors about Vioxx's risks and was responsible for the heart attack suffered by the retired agent, Gerald Barnett, 62.

Barnett began taking Vioxx after a car accident in early 2000 and suffered a heart attack in September 2002. He continued taking Vioxx until shortly before Merck stopped selling the drug in September 2004.

After less than a day of deliberations, the jury awarded Barnett $50 million in compensatory damages, and an additional $1 million in punitive damages. The case was tried before Judge Eldon E. Fallon of Federal District Court, who is overseeing 5,700 Vioxx suits.

Plaintiffs' lawyers lauded the verdict and said that it would increase pressure on Merck to reach a mass settlement.

Merck, the third-largest American drug maker, said it would appeal both decisions, but the company's shares fell almost 6 per cent.

"`We disagree with the jury's verdict. The plaintiff was at increased risk for a heart attack regardless of whether he was taking Vioxx," said Phil Beck of Bartlit Beck, Merck's lead trial lawyer in the case.

"Both the finding and the amount of damages were totally uncalled for in this case because Merck acted appropriately in providing information to the medical, scientific and regulatory communities in a responsible and appropriate manner," said Kenneth C. Frazier, senior vice president and general counsel of Merck. "While this is not the outcome we had hoped for, our commitment to defending these cases one at a time remains the same."