A key FDA whistle-blower has been ordered to testify. Dr. David Graham once publicly estimated that Merck’s painkiller Vioxx had caused 160,000 heart attacks and strokes. The FDA had sought to block Graham’s testimony, but lost that motion in federal court yesterday. Like the big drug company, the FDA is the subject of its own lawsuits over whether the government should have pulled the painkiller before Merck chose to do so.