The arthritis drug Vioxx is being pulled from the market worldwide because new research data shows it could increase the risk of heart attacks and strokes, its manufacturer announced Thursday.

Merck & Co. said clinical trials showed heart conditions and cardiovascular complications began 18 months after patients started taking Vioxx, compared to those who took dummy pills.




The three-year study hoped to show a 25 milligram dose of Vioxx prevented recurrence of polyps in the colon and rectum. Polyps can sometimes become cancerous.

"Although we believe it would have been possible to continue to market Vioxx with labelling 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," said Ray Gilmartin, Merck's chief executive officer, in a statement.

The company said patients taking Vioxx should contact their doctor to discuss discontinuing use of the drug and explore possible alternative treatments.

Medical experts said patients should not panic, since the risk of a heart attack is relatively low.

Vioxx was launched in Canada in October 1999. Merck heavily promoted Vioxx as a better option than older arthritis drugs, saying it was easier on the stomach.

Vioxx was designed to block inflammation and pain as effectively as standard nonsteroidal anti-inflammatory drugs such as ASA and ibuprofen.

In 2002 and 2003, it was the 10th most prescribed drug in Canada, down from sixth in 2001.

In 2002, there were more than 3 million prescriptions written for Vioxx in Canada. An estimated 2 million people worldwide used Vioxx in the last 12 months, according to Merck.