Patients taking Vioxx for pain relief have many alternatives, and the popular drug's withdrawal from worldwide markets yesterday should have little practical effect on clinical care, experts said.

"There is no medical condition for which Vioxx is the only option," said David Wofsy, president of the American College of Rheumatology and a physician at the University of California at San Francisco. "People should stop taking Vioxx, and contact their physicians and determine what other medications they can use."

Alternatives include other members of the COX-2 inhibitors family, which so far do not appear to increase the risk of heart attack or stroke; many non-steroidal anti-inflammatory drugs (NSAIDS); aspirin; and possibly acetaminophen, which relieves pain but does not suppress inflammation.

The dramatic nature of the announcement -- the drug's maker, Merck & Co., learned of the definitive evidence of Vioxx's hazard just a week earlier -- "is going to force a discussion about treatment" for hundreds of thousands of people with arthritis, said John H. Klippel, a physician who heads the Atlanta-based Arthritis Foundation. "We actually think that is a good thing."

In particular, he hopes practitioners and patients give a second (or first) look at non-pharmacological ways to help relieve arthritis pain. He mentioned specifically exercise and weight loss.

Although 1.3 million people in the United States, and 700,000 abroad, are using the drug, the number using it for specific diseases or lengths of time was not immediately available yesterday. It is most often prescribed for rheumatoid arthritis and osteoarthritis, and less commonly for menstrual pain, dental pain and chronic low-back pain, experts said.

Although people experience different degrees of pain relief depending on the medicine, COX-2 inhibitors overall are no better painkillers than aspirin or NSAIDS such as ibuprofen. Their chief advantage is they cause between one-quarter and one-half fewer ulcers and other forms of gastrointestinal irritation than those other drugs. (Acetaminophen, widely sold as the brand Tylenol, does not cause stomach irritation.)

Many experts believe that because COX-2 inhibitors are so expensive, they should be reserved for people at increased risk for ulcers. That includes those who have had ulcers before, the elderly, and people taking cortisone-like steroids or the blood thinner warfarin.

"For the majority of people who are not at high risk for ulcer disease, it may be more prudent to use one of the drugs with a longer track record, since the answers are not all in" on other COX-2 inhibitors, Wofsy said.

Several experts said there are no hazards in stopping Vioxx abruptly. It does not need to be tapered. They also said there is no reason to suspect any long-term or delayed effects in those who have stopped taking the drug.

That is because it works by inactivating an enzyme, COX-2, that many tissues in the body employ to make compounds called prostanoids, which have myriad functions. Once the drug washes out of the system, the affected enzyme molecules slowly regain their activity, and new ones made by cells are unaffected.

Furthermore, Vioxx's hazard appears to come from its ability to promote the clotting of blood, which is at the root of most heart attacks and strokes.

"The toxicity should not be long-lasting," said Emma A. Meagher, a physician and pharmacologist at the University of Pennsylvania School of Medicine. "It's contributing to thrombosis [clotting], which is an acute event."