Merck & Co. (MRK) attorneys unsuccessfully tried to block a plaintiff's medical expert from testifying Friday in the second product liability suit over Merck's withdrawn painkiller Vioxx.

The renowned cardiologist, Dr. Benedict Lucchesi, was part of the team that originally developed the pacemaker. Lucchesi, a professor of pharmacology at the University of Michigan Medical School (search), is expected to testify on the impact of medications on the heart.

Merck contended there is no firm scientific evidence to support Lucchesi's conclusion that brief use of Vioxx (search) caused a heart attack in the plaintiff, 60-year-old postal worker Frederick "Mike" Humeston of Boise, Idaho.

Humeston, whose doctor prescribed Vioxx for lingering pain from a Vietnam War knee wound, had been taking Vioxx for barely two months when he had a heart attack on Sept. 18, 2001.

Superior Court Judge Carol E. Higbee denied Merck's motion, saying the company's defense team had ample opportunity to take a deposition from Lucchesi or challenge his credentials prior to the start of the trial and had not done so.

Humeston's lead attorney, Chris Seeger, then called Lucchesi to the stand and questioned him at length about his expertise in cardiology and pharmacology, the study of drugs and their effects. Lucchesi discussed his medical training, ongoing work and funding for his research from the National Institutes of Health.

He was expected to testify later Friday about the circumstances of Humeston's heart attack.

Merck withdrew Vioxx from the market last September after its own research showed the popular arthritis drug doubled risk of heart attack and stroke after 18 months' use. The drug giant faces more than 5,000 lawsuits filed in state and federal courts — about half of them in New Jersey state courts — by former Vioxx users alleging the medicine harmed them.

The first trial ended last month when a Texas jury stunned Merck with a $253 million liability verdict, although that will be slashed to about $26 million because Texas caps punitive damages. Merck plans to appeal.

On Thursday, the company's lead lawyer aggressively challenged testimony of the first witness, Humeston's personal physician.

Dr. Gregory Lewer testified he believed Vioxx caused Humeston's 2001 heart attack and wouldn't have prescribed it if he knew of research linking it to cardiovascular problems.

"Nowhere in your records did you write the opinion you're giving today that Vioxx caused Mr. Humeston's heart attack," Merck lawyer Diane Sullivan told Lewer.

Sullivan, who had told jurors a day earlier that any physician who didn't know about a 2000 study that found heart attacks in Vioxx users "had to be living under a rock," asked Lewer why he hadn't seen reports of the trials in medical journals.

"The total amount of information is overwhelming. Nobody can keep up on all of it," Lewer said.

Later, Sullivan showed the jury sections of Humeston's medical records that mentioned him suffering from stress, anxiety attacks and possibly "post-Vietnam stress syndrome (search)."

The intense cross-examination came after Sullivan came under fire from Higbee for repeatedly casting aspersions on lawyers in her opening statement to the jury Wednesday, despite pretrial instructions not to do so. The judge said she would consider declaring a mistrial if it happened again.

Higbee also admonished Sullivan for talking about a Food and Drug Administration (search) memo that says cardiovascular risks are associated not just with Vioxx but with other nonsteroidal anti-inflammatory drugs.

Merck shares were up 4 cents at $28.80 on the New York Stock Exchange.