Review on LC-MS/MS Methodologies for Analysis of N-Nitrosamine Drug-Substance-Related Impurities

N-nitrosamine drug-substance-related impurities (NDSRIs) pose an important safety challenge in the pharmaceutical industry due to their potential carcinogenic and genotoxic properties. Their formation from secondary or tertiary amines within active pharmaceutical ingredients (APIs) and their structural similarity to the parent drug make their detection at trace levels a complex analytical task. Recognizing these risks, the nitrosamine class of impurities has been classified as a "cohort of concern" by global regulatory bodies, thereby requiring stringent control. This review provides a concise overview of the key factors driving NDSRI formation and highlights state-of-the-art analytical techniques, such as LC-MS/MS, for their precise quantification. In response to this risk, global regulatory authorities have mandated rigorous risk assessment and mitigation strategies. This review is an essential resource for pharmaceutical scientists and manufacturers, offering the critical knowledge needed to control these impurities and ensure the safety of manufactured medicines. It also addresses regulatory considerations for establishing the acceptable intake (AI) of NDSRIs, incorporating the recently approved CPCA concepts, and includes an overview of LC-MS/MS quantification methods for NDSRIs published between January 2022 and April 2025.