Investigation of Behavior of Forced Degradation of Lidocaine HCl by NMR Spectroscopy and GC-FID Methods: Validation of GC-FID Method for Determination of Related Substance in Pharmaceutical Formulations

The forced degradation study of lidocaine HCl was carried out according to the ICH guideline Q1A (R2). The degradation conditions were assessed to be hydrolysis, oxidation, photolysis and dry heat during 24 h, 48 h and 72 h and then the samples were investigated by GC-FID method and nuclear magnetic resonance (NMR) spectroscopy. According to these results, the degradation products were not observed in all reaction conditions during the 72 h period. Only spectral changes in the 1H and 13C-NMR spectrum were observed in hydrogen peroxide and acid degradation. As a result of this degradation, n-oxide was formed. After acid-induced degradation with HCl, the secondary amine salt was formed. Furthermore, trifluoroacetic acid (TFA) was used as the acidic media, and the decomposition products were observed. A simple and reliable gas chromatography method with flame ionization detection (GC-FID) was developed and validated for the determination of lidocaine HCl in pharmaceutical formulations in the form of a cream and injections. The GC-FID method can be used for a routine analysis of lidocaine HCl in pharmaceutical formulations and the proposed method, together with NMR spectroscopy, can be applied in stability studies.