British scientists have shown how Vioxx and other arthritis drugs, in COX-2 inhibitors category, are increasing chances of MI and stroke:
The new study, by researchers from Imperial College London and Queen Mary’s School of Medicine and Dentistry, reveals that although COX-2 inhibitors target only COX-2, they also inhibit the enzyme COX-1 within the endothelial cells that line all blood vessels.
COX-1 in these cells makes prostacyclin, which thins the blood. Where this is inhibited there is a greater chance of blood clotting, which, if the drugs are used regularly, may increase the risk of heart attacks and strokes.
Prior to the study, many in the scientific community believed that the side effects of COX-2 inhibitors were caused by inhibiting COX-2 in the endothelium and that this was reducing the production of blood-thinning agents.
The researchers found no evidence for the existence of COX-2 in the endothelium, meaning that scientists can now work on developing therapies which still target COX-2 but which do not have the adverse affect on COX-1 in endothelial cells.
The researchers found that the COX-2 inhibitors only had a significant adverse effect on COX-1 in the endothelium and not on COX-1 in other areas such as platelets in the blood. This leads them to believe that there is something about the cellular environment in the endothelium that makes COX-1 in that area vulnerable to the COX-2 inhibitors.