The then-president of Merck Research Laboratories told some colleagues he was in "minor agony" about whether the painkiller Vioxx led to heart attacks, according to a videotaped deposition played for jurors Monday in the nation's first federal trial involving the drug.

Jurors watched several depositions by now-retired Dr. Edward Scolnick. He said he initially believed a 2000 study showing Vioxx users suffered five times as many heart attacks as users of the older painkiller naproxen, sold under the brand name Aleve.

Although he changed his mind several months later and still attributes the disparity to naproxen's heart-friendly qualities rather than a defect in Vioxx, Scolnick said he wanted Merck to do other studies that were not done.

"I always worried about the safety of our drugs, and I continue to worry about it," Scolnick told plaintiffs' attorneys in the March deposition. He e-mailed some employees several years ago, "I actually am in minor agony."

Evelyn Irvin Plunkett is suing Merck (MRK), saying the drug contributed to the fatal heart attack suffered by her 53-year-old husband, Richard "Dicky" Irvin, in May 2001. He had been taking Vioxx for about a month for back pain.

U.S. District Judge Eldon Fallon said the plaintiff's side would rest its case Monday.

Merck argues that the drug wasn't responsible for Irvin's death, saying it took 18 months of Vioxx use for problems to surface, not one month. The company alleges that plaque in Irvin's artery ruptured and caused the heart attack.

This is the first federal trial over Vioxx; Merck has lost one state trial over the drug and won another, but it still faces about 7,000 lawsuits. Analysts estimate its liability could reach $50 billion.

In depositions shown to jurors Monday, Scolnick also testified that he was upset when the U.S. Food and Drug Administration wanted to put a warning label on Vioxx, which was approved in 1999. He acknowledged that such a label could hurt sales, but said the reason he objected was because "it didn't accurately reflect our data."

The FDA changed the warning label on Vioxx in February 2002 to reflect those study results showing increased risk of heart attacks and strokes.