Method validation and characterization of stress degradation products of azelastine hydrochloride using LC‐UV/PDA and LC‐Q/TOF‐MS studies

Rationale Azelastine HCl is a second‐generation H1‐receptor antagonist approved by the US Food and Drug Administration (US FDA) for treating seasonal allergic rhinitis and non‐allergic vasomotor rhinitis. This study encompasses the validation of a liquid chromatography‐ultra violet photo diode array (LC‐UV/PDA) method for the drug and its extension to liquid chromatography/quadrupole time‐of‐flight mass spectrometry (LC‐Q/TOF‐MS) studies for identification and characterization of various stress degradation products of the drug. Methods Stress degradation of azelastine HCl was undertaken under the International Council for Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) prescribed conditions of hydrolytic, photolytic, oxidative, and thermal stress. The degraded drug solutions were analyzed using Ultra Performance Liquid Chromatography (UPLC) employing a C18 (100 × 4.6 mm; 2.6 μ, Kinetex) column by isocratic elution. Detection wavelength was 241 nm. The degradation products were identified and characterized using UPLC‐MS/TOF studies, and an attempt was made to isolate one of the degradation products by solvent extraction. Results The drug was found to significantly degrade under acidic/alkaline/neutral photolytic, oxidative, and alkaline hydrolytic conditions. Six degradation products (I–VI) were identified through LC‐Q/TOF‐MS studies that were adequately resolved from the drug with the developed UPLC method. All degradation products (I–VI) were ionized in the total ion chromatogram (TIC) in the LC‐MS studies, and these were identified and characterized, and the degradation pathway of the drug was postulated. One of the oxidation products isolated from the degraded drug solution was characterized through differential scanning calorimetry, Fourier‐transform infrared spectroscopy, and nuclear magnetic resonance spectral data. Conclusions Six degradation products generated from stress degradation studies on azelastine HCl were adequately resolved through LC‐UV/PDA studies followed by method validation. These were successfully identified and characterized through LC‐Q/TOF‐MS studies, and the degradation pathways for the generation of these products from the drug have been postulated.