Stability study of the antihistamine drug azelastine HCl along with a kinetic investigation and the identification of new degradation products.

The first stability-indicating HPLC method was developed and validated for azelastine HCl (AZL). The separation of AZL from its degradation products was achieved on a C18 column using acetonitrile-0.04 M phosphate buffer of pH 3.5 (32:68, v/v) as a mobile phase with UV-detection at 210 nm and naftazone as an internal standard. The method was rectilinear over the range of 0.2-20.0 μg mL(-1) with a detection limit of 7.05 ng mL(-1). The degradation behavior of AZL was studied under different ICH-recommended stress conditions along with a kinetic investigation; also, degradation products were identified by mass spectrometry. The method was applied for the quality control and stability assessment of AZL in eye drops and nasal spray. The obtained results were favorably compared with those obtained by a comparison method.