Pfizer says it has found an increased risk of heart problems with patients taking its painkiller Celebrex, a drug that is in the same class as Vioxx, which was pulled from the market in September because of safety concerns.
New York-based Pfizer said the increased risk was found in one of two long-term cancer prevention trials, while the other trial showed no increased risk.
The National Cancer Institute, which was conducting the study for Pfizer, suspended the use of Celebrex after finding that patients taking 400 mg to 800 mg of the drug daily were found to have a risk of 2.5 times greater of experiencing heart problems than those who weren't. A separate cancer study found no increased heart risk with patients taking 400 mg of Celebrex per day.
Pfizer was conducting the trials as part of an effort to find a new application for the drug.
The news sent the stock of the giant pharmaceutical maker plunging in early trading on the New York Stock Exchange, where its shares were down $5.61, or more than 19%, at $23.37.
Both Celebrex and Vioxx, which is made by Merck & Co., are a type of drug called cox-2 inhibitors, which have become popular because of their effectiveness in treating the pain of arthritis and other ailments.
Earlier this month, the Food and Drug Administration said it was adding a warning to the labels of another Pfizer drug, Bextra, warning of potential heart problems associated with the use of Bextra in people who have recently had heart bypass surgery. Bextra is also a cox-2-inhibitor type of drug.
Celebrex is currently approved for use in the U.S. for the treatment of arthritis and pain.