British Study May Reveal Root of Adverse Vioxx Side Effects

By Nathan Abbott

Published on December 05, 2006

In an exciting development that could eventually lead to safer COX-2 inhibitors, researchers from Imperial College London and Queen Mary’s School of Medicine and Dentistry may have discovered precisely how the drugs caused those side effects.

COX-2 inhibitors such as Vioxx operate by blocking the COX-2 enzyme which is found at sites of inflammation in joints and causes the sensation of pain. Scientists had previously thought that the increased risk of heart attack and stroke carried by the drugs was related to inhibiting COX-2 in the endothelium, thereby reducing the production of blood-clotting agents. However, during their study, the researchers found no evidence of COX-2 in the endothelium at all.

Researchers discovered that the drugs were actually also inhibiting the enzyme COX-1 in the endothelium, another enzyme that helps to clot the blood. They concluded that patients taking the medicine regularly could experience problems as their blood could clot too easily within the blood vessels without the aid of the COX-1 enzyme, leading to heart attacks and strokes.

By developing new drugs that only target COX-2 inhibitors, researchers said, it may be possible to create medications that offer the same advantages as the current drugs, without the increased risk of adverse side effects.

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