Vioxx's maker, Merck & Co., pulled it from the market after a study showed that people taking it for 18 months or longer had twice the risk of heart attack, stroke or other cardiovascular problems.

About 2 million people take Vioxx, mostly for arthritis. The study was testing it for colon cancer prevention.

Here are answers for consumers:

Q. If I've been on Vioxx, do I face a higher risk of heart problems in the future?

A. "The answer to that is almost certainly 'no.' The drug's effects disappear very quickly," so stopping it should reverse risk, said Dr. Alastair J.J. Wood, professor of medicine and pharmacology and associate dean of Vanderbilt University Medical Center.

Q. Is it safe to stop taking Vioxx suddenly or should people go off the drug slowly?

A. People can and should stop taking the drug immediately. It is used only to treat arthritis pain symptoms, not the underlying disease.

Q. What made Vioxx so good for arthritis?

A. Many pain relievers called non-steroidal anti-inflammatory drugs, or NSAIDS, work against two enzymes, COX-1 and COX-2, that cause inflammation and pain. COX-1 is found in the stomach, and drugs that attack it often cause upset stomachs and ulcers. Vioxx and other so-called COX-2 inhibitors attack just that enzyme, minimizing stomach side effects.

Q. What can people take in place of Vioxx?

A. Two other COX-2 inhibitors are sold in the United States - Celebrex and Bextra, both made by Pfizer Inc. Other NSAIDs available by prescription include sulindac, sold as Clinoril and ketoprofen, sold as Orudis and Oruvail. Nonprescription NSAIDS include aspirin, ibuprofen (Advil), acetaminophen (Tylenol) and naproxen (Aleve).

Q. Can I get a refund on unused Vioxx?

A. Yes. Merck will require patients to mail back the unused 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.

More instructions and information are available through the Internet at www.vioxx.com and www.merck.com or by calling (888) 368-4699. Doctors are being asked to send back samples, and pharmacists will be contacted by Merck representatives on returning unsold inventory.