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Research Shows Cox-2 Drugs Have Different Effects

By Todd Zwillich
WebMD Medical News Reviewed By Michael Smith, MD

Feb. 14, 2005 -- New research shows that Vioxx raises blood pressure, but Celebrex apparently does not. The analysis of 19 studies, including nearly 45,500 patients, shows that the Cox-2 inhibitor class of pain relievers raises patients' risk of developing high blood pressure. However, when each of the drugs was evaluated separately, the data show that only Vioxx was associated with a rise in blood pressure. Celebrex was not.

Researchers have suspected a rise in blood pressure as one possible culprit leading to the increased heart attack and stroke risk seen among people taking this class of drugs, which includes Vioxx, Celebrex, and Bextra. The new study looked at Celebrex and Vioxx, as well as the Cox-2 inhibitor called Arcoxia, which is not available in the U.S. Bextra was not included in the analysis.

Compared with a placebo and older anti-inflammatory drugs, such as ibuprofen and naproxen, Vioxx significantly elevated blood pressure. However, the increase was small. The researchers say it's unclear if this small elevation would significantly raise the risk of heart disease. However, studies have shown that even such slight increases in blood pressure may be associated with an increased risk of heart disease.

The study by Tai-Juan Aw at Monash University in Melbourne, Australia, was published today in the online version of the Archives of Internal Medicine. The research comes just days before scheduled FDA hearings on the safety of Cox-2 drugs. Vioxx was removed from the worldwide market by Merck & Co. in September 2004 following the unveiling of data showing that Vioxx raises patients' likelihood of having a heart attack or stroke.

Questions have also been raised about Celebrex and Bextra, both of which have been associated with heart problems. An increase in heart attacks and strokes has been seen in patients taking a high dose of Celebrex -- 400 milligrams a day compared with the normal 200-milligram-a-day dose. The FDA issued a warning about Bextra after it was associated with an increase in heart problems in people undergoing heart bypass surgery.

A joint FDA advisory committee will spend three days reviewing Cox-2 drugs and could recommend restricting their use or even removing more drugs from the U.S. market. Researchers of the new study warn that they can draw only limited conclusions from the analysis, since many of the studies included in it were not specifically designed to look for differences in blood pressure.

Not all of three drugs included in the analysis affected blood pressure equally. Patients taking Vioxx had a 2.6-times greater risk of high blood pressure than those taking a placebo. Celebrex and Arcoxia were not associated with a rise in the risk of developing high blood pressure.

The results indicate increased blood pressure risk may not in fact be a problem across the entire group of Cox-2 drugs, says William B. White, MD, chief of the section of hypertension and clinical pharmacology at the University of Connecticut School of Medicine. "The Vioxx influence is going to sway the data," says White, who helped conduct four of the 19 studies included in the analysis.

But experts say there is likely more behind the apparent heart disease risk of Cox-2 drugs than simply a rise in blood pressure. While Celebrex did not appear to affect blood pressure, the high doses of the drug have still been associated with a potential increased danger of heart attacks and strokes.

"It can't just be the blood pressure that is the entire story behind heart attacks and strokes," says Eric Topol, MD, a cardiologist and Cox-2 researcher. "There is something about Vioxx that is distinctive and harmful, and we don't understand what it is," adds Topol, who is provost of The Cleveland Clinic Lerner College of Medicine.

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SOURCES: Aw, T-J., MBBS, FRACP, Archives of Internal Medicine, 2005; vol 165. William B. White, MD, professor of medicine, University of Connecticut School of Medicine. Eric Topol, MD, professor of medicine, The Cleveland Clinic Lerner College of Medicine.

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