The pharmaceutical industry is now five years into the nitrosamine era, and the expectations have only tightened. What began as a valsartan recall in 2018 became a sector-wide rethink of how we evaluate DNA-reactive impurities. The nitrosamine impurity assessment your company files in 2026 looks very different from the one filed in 2020, and regulators expect you to know why.
This guide walks through the 2026 regulatory landscape, the nitrosamine impurity assessment workflow EMA and FDA now expect, and the toxicology derivations that separate a robust dossier from a deficiency letter.
Why nitrosamine impurity assessment cannot be deprioritised
Nitrosamines are a structural class of genotoxic carcinogens. Even trace levels, parts per billion of drug substance, can exceed the Acceptable Intake for lifetime exposure. That is why every marketed medicinal product now requires a three-step nitrosamine impurity assessment regardless of manufacturing route, API age, or historic safety record.
EMA and FDA have issued more than a dozen updates since 2019, and the scope keeps expanding. The 2023 inclusion of Nitrosamine Drug Substance Related Impurities (NDSRIs), nitrosamines formed from the API itself rather than from reagents, multiplied the compound universe that must be evaluated. A 2026 nitrosamine impurity assessment therefore covers API, excipients, container interactions, manufacturing aids, and formulation-driven degradation.
The 2026 regulatory landscape
EMA expectations
EMA’s nitrosamine implementation plan is the authoritative playbook in the EU. It codifies the three-step approach (risk evaluation, confirmatory testing, corrective measures) and publishes an open list of Acceptable Intake limits for named nitrosamines. Any new NDSRI that is not on the list requires bespoke derivation, the Carcinogenic Potency Categorisation Approach (CPCA) is the agreed default when compound-specific data are missing.
FDA expectations
FDA’s Q&A guidance, most recently updated in 2024, aligns broadly with EMA but differs in some AI values and in how confirmatory testing data must be reported. The Drug Master File system means API suppliers can carry part of the nitrosamine impurity assessment burden, but marketing authorisation holders remain accountable for the final evaluation.
ICH M7 as the backbone
ICH M7(R2) remains the underlying framework for DNA-reactive impurity control. The nitrosamine programme operates as a specialised overlay on ICH M7: the same PoD logic applies, but the uncertainty factors are tighter and the TTC does not apply to the cohort of concern.
The nitrosamine impurity assessment workflow
Step 1: Risk evaluation
Start with a structured review of every nitrosation precursor in the synthesis, formulation, and packaging. Secondary, tertiary, and quaternary amines combined with nitrite or nitrous-acid sources are the classical trigger. For NDSRIs, evaluate the API itself for susceptible amine functionality. Document the outcome even when risk is judged low, EMA expects a written nitrosamine impurity assessment rationale on file.
Step 2: Confirmatory testing
Where risk cannot be dismissed, a validated analytical method at or below 30% of the AI limit must be developed. LC-MS/MS and GC-MS/MS are the typical platforms. Method validation follows ICH Q2(R2), with particular attention to recovery, matrix effects, and low-level quantification in the presence of excipients.
Step 3: Root-cause analysis
If a nitrosamine is detected, the nitrosamine impurity assessment pivots to causation. Was the source a reagent, a degradation pathway, a packaging interaction, or formulation chemistry? Isotope labelling and stability studies under stressed conditions often resolve the question.
Step 4: Corrective action
Typical mitigations include reformulation to remove nitrite scavengers, change of API synthetic route, introduction of anti-oxidants, or tightening of in-process controls. Each option carries CMC implications that must be risk-assessed against the toxicology conclusion.
Deriving PDE and Acceptable Intake for nitrosamines
For listed nitrosamines (NDMA, NDEA, NMBA, NIPEA, NDIPA, NMOR, and others) the published AI limits are authoritative. For unlisted NDSRIs, the CPCA classifies the compound into one of five potency categories based on structural alerts around the N-nitroso centre. The category drives the provisional AI, ranging from 18 ng/day (highest potency) to 1500 ng/day (lowest).
Where compound-specific carcinogenicity data exist, a de novo TD50 approach following ICH M7 is preferred. Linear extrapolation from the TD50 to a 1-in-100,000 risk for less-than-lifetime exposure scenarios can markedly relax the limit for short-duration products. The read-across assessment framework is often used to bridge from a data-rich analogue to a data-poor NDSRI.
Common sources of nitrosamine impurities
Amine-containing APIs with in-process nitrite exposure, historically the root cause of the sartan and ranitidine events. A defensive nitrosamine impurity assessment screens for nitrite specification on every starting material.
Recovered solvents carrying nitrosamine contamination, DMF and other polar aprotic solvents have been implicated when solvent-recovery columns are shared with amine-handling processes.
Tablet excipients and lubricants, stearate impurities can act as nitrite donors. This is the dominant root cause for many NDSRI findings in solid dosage forms.
Packaging interactions, blister foil primers and printing inks have been shown to leach nitrogen oxides, particularly under humid storage.
Formulation chemistry, ascorbic acid, which is often added as an antioxidant, can paradoxically catalyse nitrosation at low pH. Reformulation testing under accelerated conditions is a routine element of NDSRI control.
Building a defensible 2026 nitrosamine dossier
Regulators read the narrative, not just the numbers. A strong nitrosamine impurity assessment dossier presents the risk evaluation as a reasoned argument, shows the confirmatory testing is fit for purpose, and concludes with a transparent comparison of measured values against the AI. Where a CPCA-derived limit is used, the justification should address all five potency-category criteria.
For compounds where a de novo PDE is warranted, the document trail from PoD selection through uncertainty factors to the final limit must be fully traceable. ToxLibrary’s compound profiles (see our Toxicology Monographs) provide verified PoD inputs, historical AI precedents, and regulatory citations for more than 7,200 substances, including the emerging NDSRI catalogue.
For the broader context on how impurity chemistry drives human health risk, our earlier guide to chemical compounds and their effects is a useful orientation for cross-functional teams.
How ToxLibrary supports your nitrosamine programme
If your team is building a 2026 nitrosamine impurity assessment, managing an NDSRI investigation, or defending a CPCA-derived AI against a deficiency letter, we can help. Our toxicologists have delivered nitrosamine risk assessments across ANDAs, MAAs, and post-authorisation change submissions, and we know where reviewers probe hardest. Get in touch, the sooner the nitrosamine file is watertight, the less it costs.
