Question

Vioxx and potentially other COX-2 selective inhibitors are associated with adverse cardiovascular side effects. One year after the Food and Drug Administration approved Vioxx for the relief of arthritis symptoms, an independent research study not associated with the pharmaceutical company responsible for the production of Vioxx revealed a higher incidence of myocardial infarctions in individuals that were administered Vioxx as compared to the control group that took Naproxen. The pharmaceutical company, Merck & Co, attributed these findings to the cardioprotective effect of Naproxen. Sequential studies reported similar findings, which eventually lead to the withdrawal of Vioxx from the market. It is now clear that Vioxx causes stress on the heart that leads to a higher incidence of myocardial infarctions as compared to other nonselective COX inhibitors. In light of this information address the following:

Describe the mechanism whereby Vioxx can relieve arthritic pain.

Explain the process whereby which Naproxen can produce a cardioprotective effect.

How does Vioxx cause stress on the heart leading to a myocardial infarction?

Answer 1

• Describe the mechanism whereby Vioxx can relieve arthritic pain.

Vioxx is a COX-2 selective nonsteroidal anti-inflammatory drug (NSAID). Vioxx is a prescription medicine used to relieve signs and symptoms of arthritis, acute pain in adults, and painful menstrual cycles.

Vioxx works by blocking the enzyme that makes prostaglandins (cyclooxygenase- 2) and thereby reduces the amounts of prostaglandins. Prostaglandins are chemicals that are important in promoting inflammation and its signs--pain, fever, swelling and tenderness. As a consequence, inflammation and its accompanying pain, fever, swelling and tenderness also are reduced.

• Explain the process whereby which Naproxen can produce a cardioprotective effect. How does Vioxx cause stress on the heart leading to a myocardial infarction?

COX-2 inhibitors such as Vioxx are primarily used to treat pain in conditions such as arthritis.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.

Platelets are an integral component of cardiovascular hemostasis and express only COX-1, in contrast to endothelial cells, which express both COX-1 and COX-2. COX-1 drives production of thromboxane A2 (TXA2), which causes platelet aggregation, vasoconstriction, and an increase in vascular and cardiac remodeling. Thromboxanes increase the risk of cardiovascular events when their activity level is enhanced. Thus, inhibition of COX-1 mitigates production of TXA2, potentially lowering the risk of cardiovascular events.

Non-steroidal anti-inflammatory drugs (NSAIDs) likely increase the risk of cardiovascular events, they do so based on cyclooxygenase (COX)-2 selectivity, with greater affinity for COX-2 imparting greater risk.
Naproxen binds reversibly with COX-1 and COX-2 to exert its effects but has an increased selectivity for COX-1 inhibition, which is fivefold greater than the level of COX-2 inhibition. Naproxen has low COX-2 selectivity, instead demonstrating greater selectivity for COX-1 inhibition, Thus imparting a consistent and demonstrably favorable thromboembolic and overall cardiovascular safety.