Topical 5% Lidocaine (Lignocaine) Medicated Plaster Treatment for Post-Herpetic Neuralgia Results of a Double-Blind, Placebo-Controlled, Multinational Efficacy and Safety Trial

Background and objective: Post-herpetic neuralgia (PHN) is a distressing neuropathic pain condition mainly affecting elderly patients. Neuropathic pain symptoms can be of a burning, shooting and stabbing nature, and may continue for prolonged periods and are often poorly controlled by polymedication. The aim of this study was to evaluate the analgesic efficacy and safety of topical analgesic treatment (5% lidocaine [lignocaine] medicated plaster) compared with placebo plaster in patients with PHN. Methods: This was a double-blind, placebo plaster-controlled, parallel-group, multicentre study employing enriched enrolment with randomized withdrawal methodology. After an initial 8-week open-label, active run-in phase, responders entered a 2-week randomized, double-blind, placebo-controlled phase. The study was conducted at 33 outpatient investigational centres in 12 European countries. Patients with PHN were selected who were aged >= 50 years, had experienced neuropathic pain persisting for >= 3 months after rash healing, and had a mean pain intensity of >= 4 on an 11-point numerical rating scale. A total of 265 patients entered the open-label phase and subsequently a pre-defined number of 71 patients entered the randomized phase. Patients applied up to three 5% lidocaine medicated plasters for up to 12 hours per day. The primary endpoint of the study was time-to-exit due to a >= 2-point reduction in pain relief on two consecutive days of plaster application using a 6-point verbal rating scale. Results: Of the 265 patients entering the run-in phase, 51.7% achieved at least moderate pain relief. In the double-blind phase (full analysis set, n = 71), median times-to-exit were 13.5 (range 2-14) and 9.0 (range 1-14) days for lidocaine and placebo plaster groups, respectively (p = 0.151). For per-protocol patients (n = 34), median time-to-exit was 14.0 (range 3-14) and 6.0 (range 1-14) days for lidocaine and placebo plaster groups, respectively (p = 0.0398). Drug-related adverse events occurred in 13.6% of patients. Treatment with 5% lidocaine medicated plaster was associated with improvements in pain, allodynia, quality of life and sleep measures. Conclusions: This study adds to a growing body of evidence that the 5% lidocaine medicated plaster can be considered a valuable treatment option for patients with PHN, providing beneficial effects on pain, allodynia, quality of life and sleep, with minimal adverse effects.