The Nitrosamine “Saga”: Lessons Learned from Five Years of Scrutiny

The onset of the N-nitrosamine (NA) saga in 2018 was chiefly related to certain small dialkyl N-nitrosamines originating from the synthesis of the active pharmaceutical ingredient (API). However, the subsequent comprehensive assessments performed on APIs, formulated drug products, and packaging put a different type of NAs in the limelight: a diverse range of complex so-called nitrosamine drug-substance-related impurities (NDSRIs). They may form due to the presence of potentially nitrosatable secondary or tertiary amine moieties in APIs or API impurities and nitrosating agents formed from low levels of nitrite present as impurities. The unique properties of the amine functional group make it irreplaceable in the synthesis of APIs. While nitrite levels may be reduced, the formation of NAs in drug products cannot be completely prevented, and the class default acceptable intake (AI) of 18 ng/day currently poses significant challenges in terms of both viable control and analysis at such low levels. Even so, NA exposure through pharmaceuticals is expected to be orders of magnitude lower than the exposure via food or endogenous formation. While robust carcinogenicity data are available for many of the small, simple NAs, there is a distinct absence of such data for most NDSRIs. Many working groups have therefore been established to share data and rapidly improve knowledge (whether in terms of toxicity data, structure–activity relationships, or analytical techniques), to define best practices to assess the genotoxic potential of NDSRIs, and to advance methods to calculate AIs based on solid scientific rationales. Ultimately, to protect patients from true cancer risk and secure access to important medicines, it is crucial for manufacturers and health authorities to pursue efforts to implement NA control strategies that are equally effective and realistic. As patient safety is paramount, the pharmaceutical industry is committed to ensuring that the medicines it supplies are safe and effective. Where legitimate safety concerns exist, it is undisputed that appropriate actions must be taken, which could include withdrawal of products from the market.