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Vioxx® Increases Blood Clot Risk

Study Explains How Vioxx® Increases Heart Problems

BEVERLY and BOSTON, MA; ATLANTA, GA; AIEA, HI -- July 14, 2006 -- Using the painkiller Vioxx® may increase the risk of blood clots and atherosclerosis, a condition in which plaque or fatty deposits line the arteries, according to a new study (J Cardiovasc Pharmacol., 2006 May; 47 Suppl 1: S7-S14). The drug may also boost the chances that plaque will become unstable and rupture. Blood clots, atherosclerosis, and unstable plaques are all factors in heart attacks and strokes.

The researchers used x-rays and human blood samples to study the side effects of Vioxx® (rofecoxib). They found that the painkiller degrades and modifies low-density lipoproteins and lipids. Lipids are fats and fat-like substances in the blood. Lipoproteins are a combination of lipids bound to proteins. Vioxx® breaks down the lipids by oxidizing them to form free radicals. This process may be linked to blood clot formation and plaque instability. The oxidative breakdown of lipids by Vioxx® can be blocked by a chemical called astaxanthin, which is an anti-oxidant.

Vioxx® also easily forms a metabolite when it comes into contact with lipids and oxygen. The metabolite reacts with other molecules, including amino acids, to disrupt normal cell functions.

The researchers believe that Vioxx®'s toxic effects are due to its unique chemical properties, and not to its similarity to other drugs in the class of painkillers known as COX-2 inhibitors. Members of this class include Bextra®, which was taken off the market in April, 2005, and Celebrex®, which is still available.

Other Vioxx® Studies

Other studies have shown the harmful side effects of Vioxx®. In one three-year clinical trial, patients with early symptoms of colon cancer were treated with Vioxx® (the APPROVe study). Those who took Vioxx® had an increased risk of heart attacks and strokes compared with those who took placebos or sugar pills. In an earlier clinical trial, rheumatoid arthritis patients were checked for stomach problems (the VIGOR study). Some were taking Vioxx®, others were prescribed another painkiller. Those taking Vioxx® increased their chances of serious heart problems, including heart attacks, strokes, and blood clots.

A repeated major seller for Merck, Vioxx® represented over $2.5 billion in annual sales before it was pulled from the market in September 2004. Merck heavily promoted Vioxx® and its sales force downplayed Vioxx® risks, despite the results of the APPROVe and VIGOR reports.

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