Could a lidocaine patch plug the COX-2 gap?(Clinical Rounds)

BOSTON -- Preliminary findings from a prematurely halted trial suggest that osteoarthritis patients may have options beyond cyclooxygenase-2 inhibitors at their disposal for easing their pain.

In a poster presented at the annual meeting of the American Pain Society, Bradley S. Galer, M.D., and his colleagues demonstrated that pain relief from a 5% lidocaine patch was roughly equivalent to that from the cyclooxygenase-2 (COX-2) inhibitor, celecoxib (Celebrex), according to the findings of their randomized, controlled study.

Approved by the Food and Drug Administration in 1999 for the treatment of postherpetic neuropathic pain, the 5% lidocaine patch has been used off label to provide local relief from other types of pain.

Animal model research of osteoarthritis (OA) suggests that joint inflammation induces an up-regulation in sodium (Na) channel expression in primary afferent neurons, a process that sets the stage for chronic pain.

The ability of lidocaine to inhibit pain signals from voltage-gated Na channels makes it a potentially attractive localized approach for treating OA pain. In addition, lidocaine provides analgesia without numbing, the researchers say.

Dr. Galer and his colleagues randomized 143 patients to receive daily treatment with the lidocaine patch or with 200 mg of celecoxib. Patients in the lidocaine group applied one full-size patch to the front of the affected knee and then a third of a patch to the back of the same knee.

Participants were to be treated for 12 weeks; however, the investigation was halted early, in November 2004, because of concerns about the potential cardiovascular risks associated with the COX-2 inhibitor.