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COX-2 And The Heart: What Now? Amid still-swirling controversy, alternative strategies emerge.
The recent Vioxx recall is having ripple effects at many levels. Regulators in the U.S. and Europe are reviewing the status of all other COX-2 medications on the market, as well as those under development. The makers of these same drugs are launching new clinical trials to try to show conclusively that their particular COX-2 drug poses less cardiovascular risk than Vioxx. And people with arthritis who had relied on Vioxx for pain relief have been forced to find new alternatives for managing their chronic pain.
Since a cloud of suspicion now hangs over all COX-2 drugs, and conclusive studies on their comparative heart risks wont be complete for several years, your doctor will likely err on the side of caution when suggesting an alternative for you. As long as you can handle the stomach irritation, your doctor may recommend that you switch to an analgesic or non-steroidal anti-inflammatory drug (NSAID), either alone or in combination with a medication that can block stomach acid. Group suspicion Celebrex and Bextra are similar to Vioxx in that they reduce inflammation by blocking the cyclo-oxygenase-2 enzyme, but they dont interfere with the COX-1 enzyme that protects the stomach lining. Since they are members of the same class of drugs with similar mechanisms of action, and given whats happened with Vioxx, its reasonable to be suspicious about them all, says Steven Nissen, M.D., the Cleveland Clinic cardiologist who was among the first to call attention to the possible heart risks of Vioxx. However, the specific reasons why Vioxx causes cardiovascular problems are unclear. There are several molecules, in addition to the COX-2 enzyme, that play a role in platelet stickiness and blood clotting. And researchers can only speculate on how each COX-2 drug may differ in its effects upon these key molecules. Vioxx on trial However, when Dr. Nissen and other experts reviewed the data from the Vioxx trial, they saw signals of cardiovascular risk that, though relatively rare, were deemed serious enough to require follow-up testing. Whether such a follow-up study is done before the FDA approves a drug, is a judgment call made by the FDA. In the case of Vioxx, the FDA did not ask for a follow-up study, but instead instructed that an additional warning be added to the drug label. Vioxx remained on the market until September 2004, when a study to see if the drug could reduce the reoccurrence of colon polyps found that people taking a low dose (25mg) of the drug for 18 months were almost twice as likely to have a heart attack or stroke as those taking a placebo. What about Celebrex? Celebrex has been on the market just as long, and we havent yet seen any signal of cardiac risk, says Dr. Nissen. But then, we dont have the clinical trials to confirm this. At least not yet. In early November, Canadian health officials discovered evidence potentially linking Celebrex to 14 deaths and numerous heart-related side effects in a study of 100 adverse-reaction reports on the drug. However, both Health Canada and Pfizer, the maker of Celebrex, said that the study was limited in scope and that any conclusions based on it would be premature. In the meantime, Pfizer has announced it will launch a two-year clinical study in 2005 that will look specifically at the drugs impact on heart attack and stroke risk among 4,000 patients with osteoarthritis and a history of heart disease. Bextra: Questions still loom Then, in early November, preliminary results of a study of 5,930 patients undergoing coronary artery bypass surgery revealed that more than twice as many heart attacks or strokes were experienced among patients given Bextra.The study was later questioned by medical experts as being irrelevant to the chronic use of lower doses of the drug by arthritis patients. The next generation In October 2004, the FDA told Merck, the maker of Arcoxia, that it needed more data on the proposed drugs safety and effectiveness before it would consider approval. Preliminary findings, announced by Merck, suggested that those who took the drug for a year had no higher risk of heart attack and stroke than those who took the NSAID diclofenac. Novartis, the maker of Prexige, is being even more cautious. Though the drug is in late-stage development, the company has decided to hold off on seeking approval for the time being. This delay may be due in part to a panel of independent experts that the FDA is convening to review all COX-2 drugs (see In the News this issue). The recommendations that emerge from this body could call for significant changes in how these drugs are used and labeled, at least until new clinical trials that quantify their cardiac risk are complete.
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