Nitrosamine

Nitrosamines are a class of N-nitroso compounds — N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitroso-N-methyl-4-aminobutyric acid (NMBA) and a growing inventory of product-specific Nitrosamine Drug Substance-Related Impurities (NDSRIs) — classified by IARC as probably or possibly carcinogenic to humans and controlled at substance-specific Acceptable Intake (AI) limits in the nanogram-per-day range. The 2018 detection of NDMA in valsartan API triggered a global regulatory cascade that consolidated as ICH M7 (R2) Assessment and Control of DNA Reactive (Mutagenic) Impurities in Pharmaceuticals, with EMA, FDA, Health Canada, MHRA, PMDA and Swissmedic publishing aligned guidance.

Formation pathways are well characterised: direct reaction of secondary or tertiary amines with nitrosating agents (nitrite, nitric oxide, nitrogen oxides) under acidic conditions; contamination from nitrite-containing excipients or process water; migration from nitrocellulose-based packaging foils or printing inks; cross-contamination from shared equipment; and endogenous formation in raw materials grown with nitrate-rich fertilisers. Supplement product categories with elevated risk include amino acid blends (with proline, sarcosine, dimethylglycine, betaine), choline and lecithin products, polyamine-rich botanicals, products under acidic processing, and high-daily-intake protein powders where the intake multiplier tightens the ppm specification.

The ICH M7 framework sets a default TTC (Threshold of Toxicological Concern) of 1.5 µg/day for unstudied mutagenic impurities and substance-specific AIs for nitrosamines (NDMA 96 ng/day, NDEA 26.5 ng/day, NMBA 96 ng/day, NDBA 26.5 ng/day, others by Carcinogenic Potency Categorisation Approach where substance-specific data is absent). The product ppm specification is derived by dividing the AI by the labelled maximum daily intake. Analytical methods are LC-MS/MS with triple-quadrupole or high-resolution mass spectrometry, validated per ICH Q2(R2) at LOQs at or below 10% of the specification. Defensible programmes combine tiered supplier risk classification, change-control notification triggers, periodic surveillance testing and trend analysis — not single-result spot checks.