Safety and efficacy outcomes of long-term treatment up to 4 years with 5% lidocaine medicated plaster in patients with post-herpetic neuralgia

Objective: Prospective evaluation of the long-term efficacy and safety of the 5% lidocaine medicated plaster in patients with post-herpetic neuralgia (PHN). Research design and methods: Patients with persisting pain for >= 3 months after acute herpes zoster and a baseline pain intensity of at least 4 on an 11-point numerical rating scale (NRS 0-10) were treated with 5% lidocaine medicated plasters for up to 5 years and monitored in regular intervals. Efficacy parameters are presented for the first 4 years and include patients' recall of pain relief (6-point verbal rating scale (VRS), clinical global impression of change (CGIC), patients' global impression of change PGIC), and the global evaluations of study medication. Safety parameters (clinical examination, skin evaluation, laboratory) and adverse events (AEs) were assessed at regular visits. Clinical trial registration: KF10004/02. Results: A total of 102 patients continuing from a 1 year main study period were included in an extension phase of up to 3 years. Ten patients (9.8%) dropped out due to lack of efficacy and 9 patients (8.8%) due to treatment-related AEs; 56 patients (54.9%) left the study for non-treatment-related reasons. Twenty-seven patients (26.4%) were still under treatment after a total treatment period of 4 years. On average, a pain relief of at least 4.3 (between moderate and a lot) was achieved throughout the study. At all visits the CGIC and the PGIC were much or very much improved in about 80% of patients. At the final visit, study medication was rated at least to be good by 91% of physicians and 89% of patients. Drug-related adverse events (DRAEs) were reported in 19 of 102 patients, mainly mild to moderate localized skin reactions. There were no hints for a reduced analgesic effect or an increase of DRAEs with long-term treatment. Conclusions: This study demonstrates that long-term treatment of >= 12 months with the 5% lidocaine medicated plaster is effective and well tolerated in PHN patients. These findings support the recommendations to use the 5% lidocaine medicated plaster as baseline therapy for localized neuropathic pain after herpes zoster infection (PHN).