Influence of anatomic location of lidocaine patch 5% on effectiveness and tolerability for postherpetic neuralgia

Srinivas Nalamachu,¹ Matthew Wieman,² Leah Bednarek,² Surya Chitra<sup>2

1</sup>International Clinical Research Institute, Overland Park, KS, ²Endo Pharmaceuticals Inc, Malvern, PA, USA

Purpose: Lidocaine patch 5% is recommended as a first-line therapy for postherpetic neuralgia pain in neuropathic pain guidelines. Postherpetic neuralgia can occur anywhere on the body but often follows acute herpes zoster occurring in trigeminal and brachial plexus dermatomes. An analysis was conducted to determine whether the anatomic location of lidocaine patch 5% is associated with variations in effectiveness or tolerability in patients with postherpetic neuralgia.
Methods: This was a post hoc analysis by anatomic site of patch placement (head [including neck], trunk [chest, abdomen, back, hips], and extremities [arm, leg]) of a 4-week, multicenter, open-label study that enrolled patients with persistent pain following herpes zoster infection. Effectiveness was measured by Brief Pain Inventory (BPI) average pain intensity (0 [no pain] to 10 [worst imaginable pain]) and the BPI subscale for pain relief (0% [no relief] to 100% [complete relief]). Tolerability was assessed on the basis of patient-reported adverse events.
Results: Of 332 enrolled patients (59.6% women [n = 198]; 92.5% white [n = 307]; mean [standard deviation] age, 71.2 [13.9] years), those (n = 203) who applied lidocaine patch 5% to a single anatomic site only and had baseline and postbaseline pain score data were analyzed (trunk, n = 130; head, n = 41; extremities, n = 32). The frequency of adverse events differed significantly by anatomic location, with significantly more adverse events reported with patch placement on the head versus the extremities (P = 0.006) or trunk (P = 0.02). BPI average pain improved significantly from baseline in each of the three anatomic areas (mean score decrease, 1.50–2.04; P ≤ 0.002), with no significant difference in effectiveness by patch location.
Conclusion: Lidocaine 5% patch was effective and generally well tolerated for each anatomic area evaluated, although application to the head was tolerated less well compared with the trunk and extremities.

Keywords: acute herpes zoster, analgesia, efficacy, lidocaine, postherpetic neuralgia, topical therapies