Nancy A. Melville

September 28, 2011

September 28, 2011 (San Diego, California) — A topical formulation of the nonsteroidal anti-inflammatory drug (NSAID) diclofenac sodium 1% gel (Voltaren Gel, Endo Pharmaceuticals) shows safety and efficacy in relieving knee osteoarthritis pain in both younger and elderly patients, according to research presented here at the American Academy of Pain Management (AAPM) 22nd Annual Clinical Meeting.

Topical NSAIDs represent an attractive alternative to oral forms of the drug, providing pain relief while avoiding the various risks and adverse effects of oral NSAIDS that can be a particular concern in elderly patients, including gastrointestinal, cardiovascular, and renal adverse events.

For the study, researchers pooled data from three 12-week randomized, double-blind trials involving patients with knee osteoarthritis pain. The patients were treated with 4 g topical diclofenac (Voltaren Gel) or a vehicle 4 times daily.

The results showed that among 602 younger patients, aged 25 to 64 years, improvement after 12 weeks was greater with topical diclofenac compared with the vehicle in pain scores on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC; least squares mean [LSM], −5.8 vs −4.7; P = .007).

Scores were also improved on WOMAC physical function (LSM, −17.9 vs −14.2; P = .002), global rating of disease (LSM, −29.5 vs −23.8; P = .01), and pain on movement (LSM, −37.3 vs −29.0; P < .001).

The improvement in older patients treated with topical diclofenac was similarly improved compared with the vehicle group in terms of WOMAC pain score (P = .85), physical function (P = .70), global rating of disease (P = .86), and pain on movement (P = .81).

The only treatment-related adverse event that was more common in the treatment group compared with the vehicle group was application site dermatitis, which was seen in younger (4.0% vs 0.7%), as well as older (5.8% vs 0.4%), patients.

Voltaren was approved by the US Food and Drug Administration for osteoarthritic pain in 2007. The gel is applied to the painful joint 4 times daily, and the effects are primarily analgesic and presumably anti-inflammatory, said lead author Herbert S.B. Baraf, MD, FACP, FACR, clinical professor of medicine at George Washington University in Washington, DC.

"I would expect the therapeutic effect to be related to its half-life, and benefits rely on continued applications of the gel," he said.

Although there are no head-to-head studies comparing oral with topical NSAIDs, the treatment effects are comparable, he added. The study's objective was to determine whether the treatment or safety or efficacy were any different among the 2 age groups.

"I was personally more concerned with the adverse event profile between the 2 groups, [but] safety and efficacy were similar in the compared groups," Dr. Baraf said.

Body of Evidence

Asked by Medscape Medical News to comment on these findings, Gary M. Reisfield, MD, said the findings add to evidence supporting the benefits of topical diclofenac sodium.

"This industry-sponsored study adds to a growing evidence base in support of the safety and efficacy of topical diclofenac for osteoarthritis of the knee," said Dr. Reisfield, an assistant professor and director of the Division of Pain and Palliative Medicine at the University of Florida College of Medicine's Department of Community Health & Family Medicine in Jacksonville.

"Specifically, it demonstrates small but significant decrements in pain and pain on movement and improvements in physical function both in younger an older adults.... The major limitation of topic agents is their unsuitability for widespread or multifocal pain."

The study was supported by Endo Pharmaceuticals Inc. Dr. Baraf and Dr. Reisfield have disclosed no relevant financial relationships.

American Academy of Pain Management (AAPM) 22nd Annual Clinical Meeting: Abstract 26. Presented September 22, 2011.


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