Houston ? A prominent cardiologist testifying in Merck & Co.’s federal trial over Vioxx accused the drugmaker of engaging in scientific misconduct, suppressing clinical evidence and stifling medical discourse as it promoted the painkiller.

Dr. Eric Topol, chairman of the cardiovascular medicine department of the Cleveland Clinic, called certain aspects of Merck’s behavior “repulsive” and “appalling” during a three-hour videotaped deposition played for the jury Saturday.

Topol said Vioxx could cause heart attacks any time after a patient begins taking it, and that its risks were apparent as early as 1999, when the drug was approved. Vioxx was removed from the market last year after a study showed it doubled patients’ risk of heart attacks and strokes after 18 months of use.

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, and analysts estimate its liability could reach $50 billion.