NEW YORK (CNN/Money) -
Drug manufacturer Pfizer said Friday that its Bextra drug, seen as an alternative to Merck's Vioxx arthritis medication, may raise heart attack risk in high-risk bypass surgery patients.
Pfizer said that although clinical information on Bextra suggested no increased heart attack risk in arthritis patients, two trials in a high-risk surgery known as coronary artery bypass graft showed cardiovascular complications in patients who received Bextra alone or in combination with Parecoxib, a pain medication.
Shares of Pfizer (Research) were down 4.5 percent in afternoon trading on the New York Stock Exchange.
Additionally, the company said it is working with regulatory authorities to update the Bextra product label to warn of a rare but serious skin reaction, mainly within the first two weeks of therapy.
The drug manufacturer said the risk of a serious skin reaction is higher with Bextra than with Pfizer's other arthritis medication, Celebrex.
Pfizer said Bextra is not approved for use in surgery in the United States and that the company was conducting further studies to confirm Bextra's long-term cardiovascular safety.
However, Pfizer's Dynastat medication, an injectable COX-2 inhibitor and prodrug of Bextra, has been approved for use in surgical settings in Europe but not in the United States.
Bextra was approved for U.S. use to treat rheumatoid arthritis in adults in 2001.
Dr. Lee Simon, a rheumatologist with Boston-based Beth Israel Deaconess Medical Center and a former divisional director at the Food and Drug Administration's (FDA) Center of Drug Evaluation and Research, has studied COX-2 inhibitors.
Simon said Pfizer's announcement regarding Bextra's potential cardiovascular side-effects is a "very significant development." However, Simon cautioned that the trial was too narrow to understand whether or not the results pose wider concerns about the use of Bextra.
"My understanding is that the immediate implications are in the status of patients in the post-operative stage of the bypass procedure who may have been receiving intravenous Parecoxib and later progressed to orally taking Bextra," said Simon. "I think Pfizer has to address the concerns with a bigger trial. But Pfizer's data so far does not indicate risk of heart complications in patients taking Bextra to treat arthritis."
Earlier this month, Merck issued a worldwide recall of its blockbuster arthritis drug Vioxx after an ongoing trial confirmed the medication increases the risk of heart attack and strokes.
But Pfizer said it had reviewed heart attack risk in rheumatoid arthritis and osteoarthritis patients and saw no increased heart attack risk in patients taking the drug from six to 52 weeks.
The company said it was sending additional information to healthcare professionals about Bextra, a COX-2 product in the same class as Vioxx, a move that was prompted by increased scrutiny on Vioxx alternatives for arthritis patients.
"Bextra is an important treatment option for patients faced with debilitating and chronic pain associated with osteoarthritis and rheumatoid arthritis," said Joseph Feczko, Pfizer's president of worldwide development.
"At the same time, as is true with any medicine, all benefits and risks need to be considered by physicians when treating their patients. This communication is intended to reinforce our commitment to share information with physicians about our product."
Celebrex and Bextra are were developed by Pfizer's Pharmacia division, which the company acquired in 2002. Analysts project worldwide sales of Celebrex this year to be $3.4 billion and $1.3 billion for Bextra.