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.
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