The pharmaceutical maker Merck announced today that it is withdrawing the arthritis drug Vioxx (or rofecoxib) after they found that patients in a colon cancer trial were more likely to have heart attacks and strokes if they were on Vioxx than if they were taking a placebo. This followed soon after another study, conducted by Kaiser Permanente for the U.S. Food and Drug Administration, that found Vioxx increased the risk of heart attacks and sudden cardiac death. Here's more on that study.

What the researchers wanted to know: Do celecoxib (Celebrex), ibuprofen, naproxen (Aleve), rofecoxib (Vioxx), or other nonsteroidal anti-inflammatory drugs increase the risk of heart attacks and sudden cardiac death?

What they did: The researchers took advantage of the data Kaiser Permanente keeps on its 6 million California patients. They looked at every patient who'd been treated with a nonsteroidal anti-inflammatory drug (NSAID) between 1999 and 2001 and followed them until the end of the study period, until they left Kaiser, or until they had a heart attack or died. Each person who had a heart attack or sudden cardiac death was compared with people who hadn't to see how recently they'd taken NSAIDs and which ones they'd been on. "Sudden cardiac death" means kind of what it sounds like—your heart up and killing you.

What they found: People who took more than 25 milligrams of Vioxx daily were 3.15 times as likely to experience a heart attack or sudden cardiac death as people who'd used some NSAIDs in the past. Lower doses of Vioxx didn't seem to be as dangerous. Naproxen also slightly increased risk. Celebrex and ibuprofen had no significant effect on risk.

What the study means to you: Vioxx, especially at higher doses, may be dangerous. Since it's being withdrawn, now would be a good time to talk to your doctor about it.

Caveats: In this study of tens of thousands of people, only 10 were on high doses of Vioxx and had a heart attack or sudden cardiac death. That means there's a good chance that the study didn't get the risk of Vioxx exactly right, but the researchers can still be almost certain that it does increase risk somewhat.

Find out more: The Food and Drug Administration has a new page on Vioxx, with answers to many questions.

Information on Vioxx from the National Library of Medicine's MedlinePlus.

Merck's Vioxx page, with a link to the press release on withdrawing the drug also tells patients how to get a refund on unused Vioxx.