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Scientists Found the Possible Cause of Vioxx Side Effects

September 06, 2007

- ScienceDaily –

A group of scientists from the University of Connecticut explained the possible cause of the increased cardiovascular risks associated with Vioxx use. The report of the recently conducted study was published on the ScienceDaily web-site.

Vioxx (or rofecoxib by generic name) belongs to a group of COX-2 inhibitors, relatively new class of painkillers, widely used to relieve arthritis and other types of pain. Vioxx works by inhibiting the COX-2 enzyme, which is said to be one of the key constituents of pain mechanism. This enzyme is released in human organism in response to inflammation or injury, and causes the feeling of pain. By blocking the release of COX-2 enzyme, medications like Vioxx relieve pain.

In spite of its huge popularity on the market, Vioxx was voluntarily withdrawn from the US market by Merck, the manufacturer of the drug, in 2004. The reason for this was the data from a study called the APPROVe trial, which showed the significant increase of cardiovascular side effects, including heart attack and stroke in patients, treated with Vioxx. Since then the story of Vioxx (as well as the story of Bextra, which is another COX-2 inhibitor with similar history) remains one of the most thrilling and mysterious stories in modern pharmaceutics.

The recent study, conducted at the University of Connecticut, was initiated to reveal at least one aspect of the Vioxx story, namely, the possible cause of such serious side effects. Scientists found out that inhibiting COX-2 enzyme is followed by the significant stimulation of a protein called tissue factor or TF. The best known function of this protein is its role in blood coagulation. By other words, TF is responsible for blood clotting, which, in its turn, is the most common trigger of heart attacks and stroke in people.

Thus, the scientists presumed that stimulation of tissue factor could be the actual reason of cardiovascular risks, associated with Vioxx use. Still, this is not 100% guaranteed, since it was only the first study, which came to such a conclusion; furthermore, the conclusions were based on the trial, conducted on laboratory mice.

By the way, scientists managed to control elevated level of TF in mice by giving them certain TF-reducing drugs. Consequently, it could be possible to avoid or, at least, reduce the negative influence of Vioxx on the human cardiovascular system by combining Vioxx therapy with the medications that reduce blood clotting.

Though the results of the mentioned study will not, obviously, have significant impact on the status of Vioxx, it throws light at some aspects of the medication, which had been successfully marketed throughout the world for 5 years till the manufacturer decided to “voluntarily” withdraw it.

The story of COX-2 inhibitors is still full of unanswered questions. Some experts criticize the manufacturer for its inability to identify the potential risks of Vioxx prior to its wide marketing, which, at the end, was linked to more than 27 000 deaths. Others say that all the non-steroidal anti-inflammatory painkillers affect heart and arteries in approximately the same way, but it was only Vioxx and Bextra that were withdrawn from the market.

Anyway, the fact that scientists still continue researching issues associated with Vioxx is the evidence that COX-2 inhibitors remain among potentially promising drugs to effectively treat pain. Who knows, maybe soon new representatives of this class of medicines will be developed and approved, or even the FDA will temper justice with mercy and revise the status of Vioxx.

Nick

External resources
http://www.sciencedaily.com/releases/2007/08/070827095231.htm
http://en.wikipedia.org/wiki/Tissue_factor
http://www.vioxx.com/rofecoxib/vioxx/consumer/index.jsp
http://www.fda.gov/cder/drug/infopage/COX2/default.htm