Microdialysis as a potential tool for comparative assessment of tissue pharmacokinetics of two different patches...

Lidocaine 5% patches are approved for the treatment of post-herpetic neuralgia in adults. Little information is available on the penetration of lidocaine into skin and skin-related soft tissue, which are thought to be closer to the site where lidocaine exerts its pharmacological action on neuronal structures. This pilot study investigated subcutaneous and systemic pharmacokinetics of lidocaine during topical application of two different lidocaine 5% patches.

This randomized two-way, two-period crossover study assessed lidocaine concentrations in subcutaneous tissue (by microdialysis) and plasma of n = 5 healthy subjects during 12-hour-long applications of a recently developed lidocaine 5% patch (Laboratorios Gebro Pharma, SA, Barcelona, Spain) and a marketed reference patch (Versatis 5% lidocaine patch, Grünenthal, Brunn am Gebirge, Austria), respectively.

Lidocaine was detectable in subcutaneous tissue within 60 minutes from start of patch application, and in plasma only after a marked delay. The test formulation led to increased exposure to lidocaine in both subcutaneous tissue and plasma.

This study has underscored the potential of microdialysis to comparatively assess the pharmacokinetics of two different drug formulations and encourages its further use in this area.