Vioxx and other cox-2 inhibitors increase the production of a protein that encourages blood clotting, concludes a study published in The Journal of Experimental Medicine. The over-production of the protein, known as tissue factor (TF), could account for the increased risk of heart attacks associated with cox-2 inhibitors like Vioxx.
The Food & Drug Administration (FDA) ordered Vioxx off the market in 2004 after studies showed that people who took the drug had a higher risk for heart attack. The recall came after an analysis of patients using Vioxx linked the defective drug to more than 27,000 heart attacks or sudden cardiac deaths in the U.S. from 1999 through 2003. After Vioxx was pulled from the market, it was revealed that the FDA had tried to silence the drug expert who headed that study. Dr. David Graham, associate director for science in the FDA Drug Center’s Office of Drug Safety, told Senate investigators that he had been subjected to veiled threats and intimidation when he informed the FDA of his findings
The Vioxx debacle has spawned hundreds of lawsuits against its maker, Merck. Earlier this month, a New Jersey judge upheld a $13.5 million verdict against Merck, won by a couple who sued over injuries the man sustained after he took Vioxx.
The study published in The Journal of Experimental Medicine was conducted by researchers at the University of Connecticut Health Center. In experiments using lab mice, the researchers discovered that use of cox-2 inhibitors increased the production of TF in the heart, lungs and blood of the animals. Heart attacks and strokes are triggered by blood clots, so increase production of TF could account for the heart attack risk associated with Vioxx.
Other research has shown a link between cox-2 inhibitors and lower prostacyclin levels as a possible reason for higher cardiac risks. Prostacyclin is another protein that prevents blood clots, and it is known that Vioxx and other drugs in its class lower prostacyclin levels.
The researchers believe that other cox-2 inhibitors in addition to Vioxx also increase TF levels. One cox-2 inhibitor, Celebrex, is still on the market. It is also possible that the risk extends to non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and Aleve. Patients should use caution when taking any of these medications.
The University of Connecticut researchers also found that TF-blocking agents could reduce high levels of the protein in mice. The researchers speculated that giving patients TF-reducing agents could mitigate the cardiac risks posed by Vioxx and other cox-2 inhibitors. However, no TF-blockers have been approved for use. And despite the findings in mice, research must still prove that cox-2 inhibitors promote the production of TF in humans.