A drug company researcher says the recall of the pain-killer Vioxx may not last forever. Doctor Peter Kim, president of Merck Research Laboratories, says it could be marketed again if federal regulators conclude the benefits outweigh the risks in some cases. He testified at a joint meeting of two Food and Drug Administration advisory committees which wrap up a three-day hearing today. Vioxx was pulled after research showed an increased risk of heart-attack and stroke for long-term users. Similar drugs known as Cox-two inhibitors, like Celebrex and Bextra, are still being sold. The advisory panel could recommend that all Cox-two inhibitors be withdrawn from the market. o. pulled its blockbuster Vioxx from the market and experts raised safety concerns about similar drugs.