Pharmaceutical giant Merck bowed to several years of controversy this week by pulling Vioxx, an arthritis and pain relief drug with $2.5 billion in sales last year.

Evidence that Vioxx may increase the risk of heart attacks and strokes has been accumulating for years, but Merck had managed to sustain its viability.

Consumer groups have suggested this drug and others like it have been over sold through TV and magazine ads.

Vioxx and its chief rival, Celebrex, made by Pfizer, were originally promoted as an advance over such older anti-inflammatory painkillers as ibuprofen, the main ingredient in Advil and Motrin, and naproxen, Aleve's main ingredient.

Studies have indicated there is no evidence that the two drugs are any more effective at easing pain, but they were expected to reduce gastrointestinal side effects like ulcers and bleeding that occur in a small percentage of patients on other anti-inflammatory drugs.

Thousands of Americans die each year from such gastrointestinal complications. Celebrex and another Pfizer drug, Bextra, have never been clearly shown to reduce ulcers and bleeding.

All anti-inflammatory drugs carry some risk, especially if taken for years at a time.