Analytical Approaches for Photostability Assessment of Torsemide: A Review

ABSTRACTPhotostability testing is crucial in the quality control of pharmaceuticals, as light exposure can negativelyimpact the chemical stability, therapeutic efficacy, and safety of drug substances.Torsemide, a frequentlyprescribed loop diuretic, has UV-sensitive functional groups, including a sulfonylurea linkage and a pyridinering, that render it especially susceptible to degradation caused by light.Although torsemide has significantclinical relevance, the existing research on its photolytic behavior is sparse and frequently does not includecomprehensive mechanistic analysis, kinetic assessment, or strict compliance with regulatory standards.Thisevaluation offers a thorough assessment of the current research on torsemide photodegradation, pinpointingsignificant deficiencies in terms of compliance with ICH Q1B, inadequate characterization of photoproducts,and limited use of sophisticated analytical methods.A cohesive mechanistic framework is suggested, detailingkey degradation routes such as N–S bond breaking, hydroxylation processes, and fragmentation of the pyridinering when subjected to UV-A and UV-B radiation.The role of analytical techniques like UV–visiblespectroscopy, HPLC with photodiode array detection, and LC–MS/MS in assessing photostability is examined,with an emphasis on the development of stability-indicating methods.