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First posted October 12, 2004 Last updated October 13, 2004

Vioxx was approved by the FDA in May, 1999, for the treatment of pain and arthritis. On September 30, 2004, it was voluntarily withdrawn from the market by its manufacturer, Merck, due to some problems that were found during a study of intestinal polyps.

Vioxx is a COX-2 inhibitor (click here for an explanation). The enzyme COX, which stands for cyclooxygenase, is found in the stomach (COX-1) and in the joints (COX-2). It is also found in many other places in the body, including in platelets (responsible for clotting), stomach (responsible for making the stomach's protective coating of mucus), and in the lining of arteries (helps to prevent clotting). Note that the use in platelets (clotting) is the opposite to its use in the arteries (prevents clotting).

Merck was conducting a study of intestinal polyps, to see if Vioxx could prevent them from developing into cancer (the polyps use COX-2), with 50,000 patients enrolled in the study. There were no problems in the first 18 months of the study. In the second 18 months of the study, it was found that 16 more patients had a stroke or heart attack in the Vioxx treatment group than in the control (no Vioxx) group. While this is a very small number considering the size of the study (50,000 patients), it is still evidence of a probably problem. This prompted Merck to stop the study and withdraw the drug from the market, even for arthritis or for pain.

We think we know how Vioxx may be causing this problem. Arteries need a level of inflammation to help prevent clots from forming and blocking the arteries (the cause of strokes and heart attacks). Vioxx, while helping to block the unwanted inflammatory pain at the surgery site and unwanted inflammation in the joints, as well as not blocking the formation of protective stomach mucus, was also blocking the desirable inflammation in the arteries.

There is no evidence that other COX-2 blockers, such as Celebrex and Bextra, are similarly involved with strokes or heart attacks, but I am sure that this is being actively investigated.

If you are currently taking Vioxx, you should stop taking it and consult your doctor. I am offering my patients either an office visit to discuss their options or simply changing their prescription from Vioxx to Celebrex. In addition, Merck is offering a refund on any untaken Vioxx medication. See Vioxx.com for further information.