It was the kind of study that made doctors around the world sit up and take notice: Two popular high-blood-pressure drugs were found to be much better in combination than either alone. Unfortunately, it wasn't true. Six and a half years later, the prestigious medical journal the Lancet retracted the paper, citing serious concerns" about the findings. The damage was done. Doctors by then had given the drug combination to well over 100,000 patients. Instead of protecting them from kidney problems, as the study said the drug combo could do, it left them more vulnerable to potentially life-threatening side effects, later studies showed. Today, "tens of thousands" of patients are still on the dual therapy, according to research firm SDI. When a study is retracted, "it can be hard to make its effects go away," says Sheldon Tobe, a kidney-disease specialist at the University of Toronto. And that's more important today than ever because retractions of scientific studies are surging. Since 2001, while the number of papers published in research journals has risen 44%, the number retracted has leapt more than 15-fold, data compiled for The Wall Street Journal by Thomson Reuters reveal. Just 22 retraction notices appeared in 2001, but 139 in 2006 and 339 last year