Quantitative chromatographic method development for residual lidocaine in topical systems and biological samples.

The aim of this work was to develop and validate sensitive and efficient analytical methods for estimating systemic drug exposure and residual drug following the application of topical delivery systems. Lidocaine was extracted using a liquid-liquid extraction technique from commercial topical products and analyzed using ultra high-performance liquid chromatography. A separate LC-MS/MS method was developed for analyzing human serum samples. The developed methods were successfully applied for estimating lidocaine content in two commercial products demonstrating 97.4-104.0% for product A and 105.0-110.7% for product B. The LC-MS/MS method displayed successful analysis of lidocaine from human serum samples. The developed methods are recommended for quantifying systemic exposure and residual drug analysis of topical systems.