Risk Assessment, Detection and Control of Mutagenic Impurities in Pharmaceuticals: Emphasis on Nitrosamines

The emergence of mutagenic impurities, particularly nitrosamines and nitrosamine drug substance-related impurities (NDSRIs), has raised critical concerns across the pharmaceutical industry due to their established genotoxic and carcinogenic potential. Despite the existing regulatory frameworks, drug recalls by the USFDA continued to expose persistent gaps in the prediction, detection, and control of these impurities. The chemical origins, formation mechanisms, and risk factors associated with nitrosamines and NDSRIs remain complex, and current mitigation strategies often fail to address their variability and context-specific formation. From an analytical standpoint, quantifying these impurities at sub-ppb levels remains challenging due to matrix interference and instrumental limitations. Techniques such as LC-HRMS and GC-MS/MS provide the required sensitivity and selectivity but require rigorous compound-specific method validation. A paradigm shift toward mechanistically informed, compound-specific risk management is also essential. Structure-based computational tools such as SAR, QSAR, and QSTR and in silico tools such as TOPKAT, DOPMAT, and quantum mechanics offer preliminary hazard identification but demonstrate limited reliability when applied to chemically diverse or novel impurities. In vitro genotoxicity assays, although widely used, frequently fail to predict in vivo outcomes, particularly for complex nitrosamines, highlighting the indispensable role of in vivo studies in accurately characterizing mutagenic and carcinogenic potential, especially in borderline cases. Chemical insights into impurity formation, high-resolution analytical techniques, and integrating in vivo toxicological data provide, a comprehensive framework to enhance impurity control, ensure regulatory compliance, and safeguard long-term pharmaceutical safety.