Identification and characterization of two new oxidation degradation impurities in cinnarizine through LC‐HRMS/MS and ¹H NMR, along with in silico toxicity predictions of its degradation products

Cinnarizine (CIN) drug substance is a US FDA and EMA approved antihistaminic drug, There is no report available on CIN for the identification of degradation products and their degradation pathway. Herein, we report a stability-indicating assay method for CIN, the formation and characterization of its major degradation products using LC-HRMS/MS and ¹H-NMR techniques. CIN was subjected to oxidation, acid, base, thermal and photolytic degradation conditions. Two unknown degradation products (DP-1 and DP-2) of CIN were formed under oxidative conditions. We successfully separated these degradants using gradient elution on an Inertsil ODS 3 V column (150 × 4.6 mm, 5 μm) using mobile phase A consisting of 0.1% formic acid and the mobile phase B consisting of 0.1% formic acid/acetonitrile (20/80, v/v). CIN was labile to oxidative conditions and stable to acidic, alkaline hydrolytic, photolytic and thermal conditions. The degradation pathways were derived from the nature of the product formed under oxidative degradation conditions and available reports for confirmation of the mechanism. Since the stability-indicating assay method can be utilized for stability studies and routine quality control of CIN in both the pharmaceutical industry and research laboratories. This method has been validated in compliance with the guidelines set forth by the ICH.