The arthritis drugs known as Cox-2 inhibitors are linked to "a somewhat greater" elevation of blood pressure vs. placebo and older painkillers, according to a new study in the

Archives of Internal Medicine

.

And

Merck's

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Vioxx, which the company pulled from the market Sept. 30, "appears to confer a greater risk" of developing high blood pressure than another Cox-2 drug --

Pfizer's

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Celebrex, the researchers said.

This study is the latest addition to the data published in medical journals during recent months in advance of this week's three-day meeting of two Food and Drug Administration advisory committees. They are meeting jointly to determine if there is a so-called class effect of the Cox-2 drugs and, if so, should the drugs be banned or restricted. In the interim, the FDA has asked doctors to exercise caution in prescribing these pain relievers.

At the moment, only two Cox-2 drugs -- Pfizer's Celebrex and Bextra -- are available in the U.S. Several other drugs -- Merck's Arcoxia, Pfizer's Dynastat and

Novartis'

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Prexige -- are being considered by the FDA. These drugs are available in some foreign markets.

Although the latest study raises questions about the Cox-2 drugs, the authors do note that their research has certain qualifications.

They looked at 19 different studies, involving nearly 45,500 patients, that were published before May 2004. Then they pooled the information via a statistical method called meta-analysis to determine a common theme. This meta-analysis, they noted, "is no substitute" for the type of comparative study with patients (and researchers) not knowing who receives a drug and who receives a placebo.

"However, it is difficult to design a trial that considers the copious number of different combinations and permutations of commercially available

pain relievers," the authors said. "Because such data are not yet available, we are reliant on retrospective analysis to guide us."

The authors concluded that the general findings of higher blood pressure elevation involving Cox-2 patients and the more specific findings that Vioxx had a higher risk than Celebrex "may have the most clinical significance in the elderly," who are more susceptible to arthritis and high blood pressure.

The researchers added that although Cox-2 drugs "are a welcome addition to the therapeutic options" in treating arthritis, their use "requires caution" and "warrants further investigation." Doctors must weigh the risks and benefits, especially among their elderly patients, they added.

The research was conducted by four Australian researchers, led by Dr. Henry Krum, of Monash University in Melbourne. One researcher has been a consultant to Pfizer; another researcher has been a consultant to Pfizer, Merck and Novartis. The article was released on-line Monday in advance of the journal's March 14 publication date.