The future of the arthritis treatments Celebrex, Bextra and Vioxx may rest on a question of basic science: Why would all three drugs increase the risk of heart attack and stroke, at least at high doses? Two competing theories seem to be shaping the thinking of the U.S. Food and Drug Administration advisory panel that is likely to decide the fate of these medicines. The first, posited six years ago by University of Pennsylvania pharmacologist Garret FitzGerald, is that the drugs make blood more likely to clot by their very mechanism, the inhibition of the enzyme cycloxygenase 2 (Cox-2). Another idea is that the heart risk is the result of an increase in blood pressure. Many older arthritis drugs, such as Aleve and Advil, cause elevations in blood pressure, and these could lead to heart attacks. Vioxx, the drug recalled by Merck (nyse: MRK - news - people ), caused a fairly big increase in blood pressure, but Celebrex, made by Pfizer, does not appear to do the same.
