BOSTON -- The arthritis drug Vioxx may not be the only drug of its type that raises the risk of heart attack and stroke.

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Fact Sheet: More On Vioxx
Video: Merck Recalls Popular Arthritis Drug

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Scientists cite studies conducted five years ago when Merck's Vioxx and Pfizer's Celebrex were approved by the Food and Drug Administration. The research suggests that the same mechanism that inhibits inflammation and makes the drugs easier on the stomach than other painkillers also blocks a substance that prevents heart problems.

Vioxx -- which was heavily marketed as an arthritis drug -- was pulled from the market last week. Its manufacturer said research had found it doubled the risk of heart problems.

When Merck voluntarily withdrew Vioxx last week, FDA officials said other, similar prescription drugs were safe, and that the mechanism underlying them wasn't known. But European regulators aren't so sure. The European Medicines Agency in London said it's going to review drugs similar to Vioxx.

The studies contradicting that statement were led by a University of Pennsylvania cardiologist and funded by the drug companies. They will be published in the New England Journal of Medicine later this month.

In the journal, the cardiologist who led the studies says he thinks the problem with Vioxx may also apply to Celebrex and to a newer Pfizer drug, Bextra.

Both remain on the market, and Pfizer said the drugs are safe.

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Patients who are currently taking Vioxx should contact their health care providers to discuss discontinuing use of the drug and possible alternative treatments. For more information, visit merck.com, vioxx.com, or the Food and Drug Administration's Vioxx page. Patients and health care professionals with questions can also call (888) 36-VIOXX (1-888-368-4699).

Patients can get a refund on unused Vioxx by mailing back the remaining drug in the original container, along with a pharmacy receipt, to:

NNC Group
Merck Returns
2670 Executive Dr.
Indianapolis, IN 46241

A note with the patient's name, address and phone number should be included. The company will reimburse the cost of the full prescription plus regular shipping.