Nitrite-Driven Nitrosamine Formation in Pharmaceutical Systems: A Water-Mediated Risk Framework and Control Strategies

Abstract

N-nitrosamines are genotoxic impurities whose detection in several marketed medicines has raised major safety concerns for pharmaceutical systems. They form when nitrosating agents - particularly nitrite - react with amine precursors under favourable physicochemical conditions. This review examines nitrite-driven nitrosamine formation with an emphasis on water-mediated pathways in pharmaceutical systems. It outlines the underlying nitrosation chemistry, including classical acid-catalysed routes and alternative chloramine-mediated and oxidative mechanisms, and evaluates how water sources, water-purification processes and physicochemical parameters (pH, temperature and moisture) influence formation. Particular attention is given to how trace nitrite in pharmaceutical water systems generates nitrosamines even at very low concentrations. Analytical methods for nitrosamine and nitrite determination are reviewed, highlighting advances in LC-MS/MS, GC-MS and high-resolution mass spectrometry for ultra-trace quantification. Risk-based mitigations are discussed, including nitrite control, water-quality management, raw-material assessment, process optimisation and lifecycle monitoring. A key regulatory gap identified is the absence of defined nitrite limits for pharmaceutical water in pharmacopoeial standards. Overall, the review offers a mechanistic, risk-oriented framework for understanding nitrite- and water-related nitrosamine formation and argues for stricter, precursor-focused control measures to safeguard pharmaceutical product quality and safety. Keywords: Nitrite, Nitrosation mechanism, Water-mediated reactions, Nitrosamine formation, Pharmaceutical water systems, Regulatory risk assessment