Updated

Merck & Co. (MRK) rested its case Wednesday in the first federal trial involving the painkiller Vioxx after a pathologist testified that the drug played no role in a man's fatal heart attack.

Closing arguments were set for Thursday in the trial stemming from a lawsuit filed by Evelyn Irvin Plunkett, whose 53-year-old husband Richard "Dicky" Irvin died in 2001 after taking Vioxx for back pain for a month. She says Whitehouse Station, N.J.-based Merck failed to issue safety warnings and that Vioxx caused his heart attack.

Dr. Thomas M. Wheeler, the head of Baylor College of Medicine's pathology department, testified Wednesday that Irvin's sudden death was caused by plaque that ruptured in an artery, causing a blood clot that led to the heart attack. He said Vioxx did not contribute to Irvin's death.

Under cross-examination, Wheeler said he had heard of an article by Merck scientists saying that Cox-2 inhibitors such as Vioxx could increase the risk of destabilizing plaque. But he said it was a theoretical possibility that deserved more study and that there was no clinical evidence.

Earlier Wednesday, Merck's vice president for clinical research testified that the company never misled doctors and the public about studies linking heart attacks to Vioxx.

Dr. Alise Reicin said the company kept defending the drug's safety -- despite concerns raised by the Food and Drug Administration and a renowned cardiologist's article in a medical journal -- because Merck looked at several studies and simply didn't believe Vioxx caused heart attacks.

Although a 2000 study showed Vioxx users suffered five times as many heart attacks as users of the older painkiller naproxen, Merck explained the results by saying that naproxen has a protective effect on the heart.

A month after that study was released and again a year later, Merck issued press releases entitled "Merck confirms favorable cardiovascular safety profile of Vioxx."

"We were telling the public what we believed," Reicin testified.

But the FDA sent Merck a warning letter in 2001 saying that claim was "simply incomprehensible" and the idea that naproxen protected against heart attacks was just a hypothesis. The FDA also said Merck's marketing campaigns were "false, lacking in fair balance and otherwise misleading."

Merck voluntarily took Vioxx off the market in September 2004 after results of a long-term study showed the drug doubled risk of heart attack or stroke if taken for 18 months or longer.

This is the first federal trial over Vioxx; Merck has already lost one state trial over the drug and won another, but it still faces about 7,000 lawsuits. The Irvin case was moved to Houston from its original venue of New Orleans because of damage from Hurricane Katrina.