Efficacy and tolerability of a 5% lidocaine medicated plaster for the topical treatment of post-herpetic neuralgia: results of a long-term study

Objective: Evaluation of long-term efficacy and safety of the 5% lidocaine medicated plaster for neuropathic pain symptoms in patients with post-herpetic neuralgia (PHN). Materials and methods: Design - a 12-month, open-label, phase III study with an open-label extension conducted at 34 outpatient clinics in 12 European countries. Patients - aged >= 50 years, newly recruited (average pain intensity >= 4) or pretreated with the 5% lidocaine medicated plaster in a previous study. Interventions - application of up to three 5% lidocaine medicated plasters dependent upon size of the painful area for up to 12 hours per day. Outcome measures - efficacy measures included patients' recall of pain relief and pain intensity in the previous week. Adverse events (AEs) were also reported. Results: 249 patients participated in the 12-month study, 247 were analysed (full analysis set, FAS). Newly recruited patients had a mean average pain intensity (11-point numerical rating scale [NRS]) of 5.9 +/- 1.4 at baseline, which decreased to 3.9 +/- 1.6 at week 12 and remained stable at 3.9 +/- 2.3 until the end of the 12-month study. In pre-treated patients, pain intensity decreased further from baseline (3.9 +/- 1.9) to study end (3.4 +/- 2.0). Pain relief values were consistent with pain intensity reductions and were sustained in patients continuing treatment in the extension phase (mainly >= 24 months treatment in total). The most common AEs tended to be infections such as bronchitis and nasopharyngitis. Forty-eight drug-related adverse events (DRAEs), mainly mild to moderate localised skin reactions, occurred in 31 (12.4%) patients in the first 12 months. The profile of DRAEs was similar in the extension phase. Conclusions: This study suggests that long-term treatment with the 5% lidocaine medicated plaster may provide substantial and maintained reductions in pain intensity, and that it is continuously well tolerated in patients suffering from peripheral neuropathic pain associated with previous herpes zoster infection. These findings support the use of the 5% lidocaine medicated plaster as one of the first-line therapies in this population.