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Lidocaine Patch Found Effective for Knee Pain

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WEDNESDAY, March 30 (HealthDay News) -- People who suffer from osteoarthritis of the knee may not need to rely on potentially risky cox-2 drugs to alleviate their pain. A simple patch placed on the affected area may provide comparable relief, results of a new study suggest.

The study compared the efficacy and safety of Lidoderm, a transdermal patch containing 5 percent lidocaine, with celecoxib, popularly known by the brand name Celebrex. At six weeks, patients using the patch experienced similar relief from pain as those who were taking celecoxib, according to Dr. Alan Kivitz, founder of the Altoona Center for Clinical Research in Duncansville, Pa., and a co-author of the study.

That observation could lead to an appealing treatment alternative for millions of Americans who suffer from osteoarthritis of the knee, he said.

"For me, the most important thing is to have [treatment] options available," Kivitz said Wednesday during a teleconference sponsored by the American Pain Foundation, a nonprofit advocacy group based in Baltimore.

Researchers were to present the findings late Wednesday at the 24th annual scientific meeting of the American Pain Society in Boston. Endo Pharmaceuticals Inc., maker of the Lidoderm patch, funded the study.

Osteoarthritis of the knee is a leading cause of disability in the United States. In 2001, more than 13.5 million adults reported having knee joint pain, swelling and stiffness, according to the American Academy of Orthopaedic Surgeons.

Initially, investigators intended to enroll a total of 200 patients in a randomized, open-label study comparing lidocaine and celecoxib. But in November 2004, Endo Pharmaceuticals voluntarily halted the study before it was fully enrolled because of concerns about the safety of cox-2 inhibitors.

Consequently, the results are preliminary, Kivitz cautioned.

Questions about the cox-2 class of painkillers began to surface after Merck & Co. pulled its arthritis drug Vioxx from the market on Sept. 30, 2004, on data suggesting a link to heart attack and stroke risk. Two other cox-2 drugs, Celebrex and Bextra, also have been implicated for cardiovascular risks.

In February, a federal advisory panel recommended keeping all three drugs on the market. Its conclusion suggests the benefits of these drugs outweigh the risks. Still, the controversy has created a substantial amount of confusion and anxiety.

"The fall of 2004 has really set us back," Micke Brown, the American Pain Foundation's public outreach manager, said during Wednesday's teleconference. "Both the medical profession and the public at large are confused."

And while some people are sticking with cox-2 therapy, others are discontinuing the use of those drugs without consulting their physicians first, sometimes with unfortunate consequences.

During the teleconference, Dr. Steven Stanos, medical director of the Rehabilitation Institute of Chicago's Chronic Pain Care Center, said he had seen two patients who developed kidney problems after switching to over-the-counter pain medication.

Kivitz and his colleagues were not seeking a cox-2 alternative when they began the study comparing the lidocaine patch and celecoxib. They merely speculated that Lidoderm, approved by the U.S. Food and Drug Administration in 1999 for the treatment of postherpetic neuralgia, a painful complication of shingles, would produce the same analgesic response when applied to arthritic joints.

"With all of the concern about cox-2 inhibitors, the study took on new potential meaning," Kivitz acknowledged.

A total of 143 patients suffering from osteoarthritis of one or both knees were enrolled in the study before its termination. Sixty-nine received lidocaine patches; 74 were treated with 200-milligram celecoxib.

After six weeks of treatment, 54 percent of the lidocaine patients and 62 percent of the celecoxib patients experienced a 30 percent or greater improvement in pain intensity.

"This is what we call clinically meaningful," Kivitz said.

As with any FDA-approved medication, physicians are free to prescribe the lidocaine patch for osteoarthritis of the knee. It would be considered an "off-label" use, since the therapy is not approved for that purpose.

And while further research is needed to bear out the safety and effectiveness this approach, Kivitz said the findings should give patients hope that other pain-relief options are being explored. "It's meant to give encouragement," he said.

More information

The National Institute of Arthritis and Musculoskeletal and Skin Diseases has more on osteoarthritis.

SOURCES: Alan Kivitz, M.D., founder, Altoona Center for Clinical Research, Duncansville, Pa., Micke Brown, BSN, R.N., public outreach manager, American Pain Foundation, Baltimore; Steven Stanos, D.O., medical director, Chronic Pain Care Center, Rehabilitation Institute of Chicago; American Academy of Orthopaedic Surgeons, Rosemont, Ill.; March 30, 2005, teleconference, American Pain Foundation; abstract, 24th annual scientific meeting, American Pain Society, Boston
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