BOSTON, Ma. (Mar. 30) - A lidocaine patch 5% (LidodermR) provides similar pain relief as 200 mg/day of cyclo-oxygenase-2 (COX-2) inhibitor celecoxib in patients with osteoarthritis (OA) of the knee, according to a randomized, open-label study presented Wednesday at the 24th Annual Scientific Meeting of the American Pain Society in Boston, Massachusetts.¹

Due to the safety concerns surrounding COX-2 inhibitors that arose during the fall of 2004, the study's sponsor, Endo Pharmaceuticals, stopped enrollment prior to reaching the original target of 200 patients. An analysis of data after 6 weeks of treatment, however, showed that 54% of patients (30 of 56) who used the analgesic patch experienced a 30% or greater improvement in average daily pain intensity, compared with 62% (39 of 63) in the celecoxib group. In addition, there were clinically meaningful reductions in pain in both treatment groups at week 12.

"Although these results will need to be confirmed with further randomized controlled trials, the potential of Lidoderm to treat osteoarthritic knee pain is promising," says study author Alan Kivitz, MD, founder of the Altoona Center for Clinical Research in Altoona, Pennsylvania.

While the mechanisms responsible for causing pain in OA patients are not entirely understood, animal models suggest that the upregulation of neuronal sodium channels induced by joint inflammation results in hyperalgesia. Lidocaine exerts its analgesic effects by blocking sodium channels.

The US Food and Drug Administration approved the lidocaine patch in 1999 to treat post-herpetic neuralgia. Steven Stanos, DO, medical director of the Rehabilitation Institute of Chicago Pain Care Center in Illinois, tells CIAOMed that "the neurons affected by joint inflammation are similar to those affected by post-herpetic neuralgia, suggesting that the lidocaine patch may be effective in knee OA patients." He adds that local administration afforded by this treatment has certain advantages. "Patch systems may play an additional role in the ability to target [pain] without side effects."

Patients in the study underwent a 7- to 14-day washout period during which all analgesic medications and supplements were discontinued. Patients with an average daily pain intensity score of >e; 5 on a scale of 0 to 10 for 3 of 5 consecutive days and an OA severity score of <e; 7 on a scale of 0 to 24 were then randomized to one of two treatment groups for a 12-week course of therapy. One group used a full Lidoderm patch on the front and one-third of a patch on the back of each affected knee once daily for 24 hours, while the other group used celecoxib 200 mg once daily. The most common adverse events (AEs) were itchiness or redness at the patch site. There were no discontinuations due to treatment-related AEs in the celecoxib group, but Dr. Kivitz points out that there were not enough patients to detect cardiovascular safety signal.

Lidocaine patch also useful as adjunct to NSAIDs

In a related post-hoc analysis,² the addition of a lidocaine patch to a coxib or traditional NSAID in patients with OA and chronic low back pain resulted in significant improvements in pain intensity and pain-related quality of life. The patch "may provide clinicians with a new treatment option for OA pain and chronic low back pain that is effective and safe when used in combination with COX-2 inhibitors and NSAIDs," the study authors conclude.

References:

1. Galer, B, Kivitz A, Fairfaxm M, et al. A randomized, open-label study comparing the efficacy and safety of lidocaine patch 5% with celecoxib 200 mg in patients with pain from osteoarthritis of the knee. Presented at: 24th Annual Scientific Meeting of the American Pain Society; March 30-April 2, 2005; Boston, Massachusetts. Poster No. 771.
2. Galer B, Oleka N and Gammaitoni AR. Efficacy and safety of the lidocaine patch in osteoarthritis and chronic low-back pain in patients receiving suboptimal pain relief from COX-2-selective or traditional NSAID therapy. Presented at: 24th Annual Scientific Meeting of the American Pain Society; March 30-April 2, 2005; Boston, Massachusetts. Poster No. 768.