NEW YORK (AFP) - US pharmaceutical giant Merck announced a worldwide withdrawal of its blockbuster arthritis drug Vioxx after a study showed it increased the risk for strokes and heart attacks.
Vioxx has been marketed in more than 80 countries and produced sales of 2.5 billion dollars in 2003.
"We are taking this action because we believe it best serves the interests of patients," said Merck and Co. chairman Raymond Gilmartin.
"Although we believe it would have been possible to continue to market Vioxx with labeling that would incorporate these new data, given the availability of alternative therapies, and the questions raised by the data, we concluded that a voluntary withdrawal is the responsible course to take."
The decision was based on data from a trial designed to evaluate a possible new use for Vioxx -- preventing the recurrence of colorectal polyps. After 18 months of treatment, the data showed increased relative risk for cardiovascular events, such as heart attack and stroke.
Peter Kim, president of Merck Research Laboratories, said, "While the cause of these results is uncertain at this time, they suggest an increased risk of confirmed cardiovascular events beginning after 18 months of continuous therapy. While we recognize that Vioxx benefited many patients, we believe this action is appropriate."
Merck, based in Whitehouse, New Jersey, said it has informed the US Food and Drug Administration and regulatory authorities in other countries of its decision.
"Merck did the right thing by promptly reporting these findings to the FDA and voluntarily withdrawing the product from the market," said acting FDA Commissioner Lester Crawford.
"Although the risk that an individual patient would have a heart attack or stroke related to Vioxx is very small, the study that was halted suggests that, overall, patients taking the drug chronically face twice the risk of a heart attack compared to patients receiving a placebo."
The FDA said in a statement it was releasing a public health advisory to inform patients of the withdrawal "and to advise them to consult with a physician about alternative medications."
The company also said it is notifying health care practitioners in the United States and other countries where Vioxx is marketed, while advising people taking the medication "to discuss discontinuing use of Vioxx and possible alternative treatments."
Merck shares plunged 11.78 dollars, or 26 percent, to 33.29 dollars at 1500 GMT amid concerns of a severe impact on the company.
Shares of fellow Dow component Pfizer, which makes the rival arthritis medication Celebrex, rallied 34 cents, or 1.3 percent, to 30.52.