The U.S. Food and Drug Administration failed to protect the public from Merck & Co. Inc.'s (MRK.N: Quote, Profile, Research) now-withdrawn painkiller Vioxx and is incapable of guarding America from dangerous drugs, a veteran FDA researcher told Congress on Thursday. Dr. David Graham, a 20-year FDA scientist who had warned about heart risks with the Vioxx arthritis pill, called the agency’s oversight of the drug “a profound regulatory failure.” Concerns about a link between the medication and heart problems were building during more than four years on the market. The FDA required a warning about possible heart risks but felt the drug’s benefits, few ulcers and less stomach bleeding, made it worth keeping on the market. Merck Chief Executive Raymond Gilmartin said the company had believed wholeheartedly in Vioxx and had followed a rigorous scientific procedure every step of the way.