Topical lidocaine patch 5% may target a novel underlying pain mechanism in osteoarthritis

Abstract

Recent literature and animal research has provided insight to potentially new analgesic targets for managing osteoarthritis (OA) pain. Primary afferent neurons located in affected joints express excessive amounts of abnormally functioning sodium (Na) channels on their surface in response to the inflammatory process. These Na channels may play an integral role in production of pain and hyperalgesia. Hence, the authors set out to conduct a 2-week, open-label, multicenter proof-of-concept study to evaluate the effectiveness and safety of lidocaine patch 5% monotherapy in adults with OA pain of the knee (n = 20). Patients with OA of one or both knees who were experiencing inadequate pain relief (defined as an average daily pain intensity of > 4 on a 0 to 10 pain scale) with their current analgesic regimen (i.e. APAP, NSAIDs, COX-2 inhibitors, tramadol) were enrolled and had all analgesic medications discontinued. Treatment with the lidocaine patch 5% resulted in significant improvements in the Western Ontario and McMaster Universities OA Index (WOMAC) pain, stiffness, physical function subscales and composite index (48.4, 41.1, 47.0, and 46.8% improvements respectively, p < 0.01). In addition, significant improvement was noted for pain intensity, pain relief, and pain interference with quality of life as measured by the Brief Pain Inventory (p < 0.05). The lidocaine patch 5% was generally well tolerated and no patients discontinued due to treatment-related adverse events. Given the open-label design, lack of a control group, and small sample size, the findings from our pilot study need to be confirmed by larger randomized controlled trials. Topical lidocaine patch 5% may provide clinicians with a novel, non-systemic therapy for OA pain with a unique mechanism of action.

Symptom Profiles Differ in Patients With Neuropathic Versus Non-neuropathic Pain

“…6,15,18,21,23,24,44 Analyses of changes with lidocaine patch 5% treatment in several of these studies for NPS items and scales and of the relationships between NPS items and physical and emotional functioning have been reported previously. 2,19,22,26,27 All participants provided informed consent before any study procedures were initiated.…”

Assessment of pain quality in chronic neuropathic and nociceptive pain clinical trials with the Neuropathic Pain Scale

“…The data for this study were obtained from 6 open-label trials of the analgesic. 1,5,[10][11][12]21 Except for some very minor variations, the procedures used in these studies were identical. Variations across the studies included (1) minor differences in the lengths of the trials, with post-treatment data available at 2 weeks for 4 of the studies and at 3 weeks for 2 studies and (2) slight differences in inclusion criteria (detailed below in the Methods section) as a result of differences in diagnoses.…”

Do Pain Qualities and Spatial Characteristics Make Independent Contributions to Interference With Physical and Emotional Functioning?

“…2,3,[9][10][11]14,15,30 Analyses of changes with 5% lidocaine patch treatment in several of these studies in ratings of pain qualities and locations have been previously reported, 1,10,11,13,18 as have analyses concerning the differences between diagnostic groups in response to the pain descriptor ratings. (Dworkin RH, Jensen MP, Gammaitoni AR, Olaleye DO, Oleka N, Galer BS, Symptom profiles differ in patients with neuropathic vs. non-neuropathic pain.…”