On the eve of the second trial over its painkiller Vioxx, drug giant Merck & Co. on Friday reasserted that it plans to aggressively fight the mounting lawsuits over the withdrawn drug, despite recently saying it might settle some suits.

Kenneth C. Frazier, Merck’s general counsel and senior vice president, also tried to reassure investors that liability over Vioxx — estimated by analysts at up to $50 billion — isn’t a threat to the Whitehouse Station, N.J.-based company.