In a recent letter to Merck & Co., the Food and Drug Administration (FDA) requested that the drug maker stop misrepresenting Vioxx's drug safety profile and diminishing its side effects. Of particular concern to FDA officials was Merck's cursory treatment of the risks of heart problems and excessive bleeding in patients taking Vioxx. The FDA has required Merck to send an FDA-approved letter to health care professionals detailing the risks.

The FDA's warning letter came shortly after similar warnings to Merck's primary competitors, Pfizer and Pharmacia Corp, manufacturers of the popular arthritis drug, Celebrex.

Vioxx has been in the news recently following a major clinical trial which found more heart problems, strokes, and blood clots associated with Vioxx than with more traditional arthritis medications like naproxen.