Usage Examples
- The risk evaluation found a secondary amine in the API and nitrite in the excipient, so we skipped ahead to confirmatory testing on the finished product.
- We cannot default to the 1.5 microgram per day TTC on this one, it is an N-nitroso compound, so it needs a substance-specific AI.
- The enhanced Ames test came back negative, so we can control it at 1.5 micrograms per day and file the variation with that limit.
What is Nitrosamine Impurity?
Nitrosamine impurities are N-nitroso compounds that form in or contaminate drug substances and drug products; ICH M7(R2) places them in the cohort of concern, so each needs a substance-specific acceptable intake, not the generic 1.5 microgram threshold.
Nitrosamine impurities became their own regulatory category because the standard impurity arithmetic does not protect against them. ICH M7(R2), adopted 3 April 2023, sets a Threshold of Toxicological Concern of 1.5 micrograms per day for mutagenic impurities, then carves out a group of structures so potent that intakes below that threshold still carry significant theoretical carcinogenic risk. N-nitroso compounds sit in that carve-out, the cohort of concern.
Nitrosamine impurities are assessed across the whole product, not just the synthesis route: nitrosating agents meeting secondary or tertiary amines, disinfected water, oxidised hydrazines, contaminated recovered solvents, nitrite in common excipients, and nitrosatable amine groups on the API itself. Scope stops in three places: ICH S9 advanced-cancer products and impurities shown non-mutagenic in vivo fall back to ICH Q3A(R2) and Q3B(R2), and anything under 10 percent of its AI needs no specification.
Nitrosamine impurities are worked in three steps under EMA's call for review: risk evaluation (step 1), confirmatory testing (step 2), and risk mitigation through variations (step 3). Products approved after 26 September 2019 without a risk evaluation in the original application still owe the step 1 deadlines. Confirmatory testing is generally run on the finished product, with API and raw material testing added where the evaluation points upstream.
Not to be confused with
- Elemental impurity (ICH Q3D)
- an inorganic element controlled against a Permitted Daily Exposure, with a 30 percent control threshold deciding whether extra controls are needed. Nitrosamines are organic, cohort-of-concern, and limited in nanograms. A completed Q3D risk assessment provides no nitrosamine coverage whatsoever.
- Mutagenic impurity generally (ICH M7)
- most mutagenic impurities can be controlled at the 1.5 microgram per day TTC. Nitrosamines are the exception the guideline names by structure, which is why a compliant M7 control strategy can still be wrong by orders of magnitude for an N-nitroso compound.
- N-nitroso API impurity (NO-API)
- formed by nitrosation of the drug substance's own amine group during formulation or storage, so it is unique to your molecule and has no reference standard waiting on a shelf. NDMA and NDEA are small contaminants carried in from the process; a NO-API is your API with a nitroso group attached.
- Nitrite
- the nitrosating precursor found as an impurity in many common excipients, not the impurity being regulated. A low excipient nitrite result characterises risk, it does not demonstrate compliance, because EMA warns N-nitroso API impurities can exceed the AI even when nitrite levels are very low.
The obligations below are the EU framework under the Article 5(3) referral, anchored on the ICH M7(R2) toxicology.
What you must do
- 1Do not apply the 1.5 microgram per day TTC by default to an N-nitroso compound, because the cohort of concern comprises aflatoxin-like, N-nitroso and alkyl-azoxy structures whose acceptable intakes are significantly lowerICH M7(R2) Section 3
- 2Evaluate every identified root cause, covering nitrosating agents used alongside secondary or tertiary amines, nitrite formation from nitro-aromatic precursors, disinfected water, oxidised hydrazines, contaminated recovered or vendor-supplied materials, and nitrite in excipients reacting with a nitrosatable APIEMA/409815/2020 Rev.23 Q&A 4
- 3Run step 2 confirmatory testing on the finished product, extending to API, intermediates, starting materials, solvents, reagents and excipients where the risk assessment identifies them as a potential sourceEMA/409815/2020 Rev.23 Q&A 8
- 4Establish a substance-specific acceptable intake using the Carcinogenic Potency Categorization Approach unless more robust data override it, or control at 1.5 micrograms per day on a negative GLP-compliant enhanced Ames testEMA/409815/2020 Rev.23 Q&A 10
- 5Submit the resulting changes to manufacturing process, controls, formulation, raw materials or packaging as timely variations, and add the corresponding limit to the finished product specificationEMA/409815/2020 Rev.23 Q&A 13
Common mistakes
Defaulting to the 1.5 microgram per day TTC
EMA states plainly that the TTC value cannot be routinely applied to N-nitrosamines, because the AI must correspond to a theoretical excess cancer risk below 1 in 100,000 over a lifetime. A specification built on the TTC can be orders of magnitude too permissive and will not survive assessment.
Reading a clean excipient nitrite result as no risk
EMA warns that N-nitroso API impurities can form above the AI even when nitrite levels in the excipients are very low, and that formation continues during storage. The AI has to hold to the end of shelf life, so a release-only argument leaves the stability question open.
Treating the risk evaluation as closed once step 1 was filed
the obligation is lifecycle-long, and any later change that affects risk (new supplier, process change, new packaging) reopens it. Products approved after 26 September 2019 whose risk evaluation was never assessed in the application still owe the call for review deadlines.
When This Matters
- The risk evaluation found a secondary amine in the API and nitrite in the excipient, so we skipped ahead to confirmatory testing on the finished product.
- We cannot default to the 1.5 microgram per day TTC on this one, it is an N-nitroso compound, so it needs a substance-specific AI.
- The enhanced Ames test came back negative, so we can control it at 1.5 micrograms per day and file the variation with that limit.
Frequently Asked Questions
A substance-specific acceptable intake applies, not the generic 1.5 microgram per day TTC. ICH M7(R2) places N-nitroso compounds in the cohort of concern, and EMA states the TTC value cannot be routinely applied. The AI corresponds to a theoretical excess cancer risk below 1 in 100,000 over a lifetime of daily exposure.
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Sources & References
- ICH M7(R2) Assessment and Control of DNA Reactive (Mutagenic) Impurities in Pharmaceuticals
- EMA Questions and answers on the Article 5(3) referral on nitrosamine impurities in human medicinal products (EMA/409815/2020 Rev.23)
- FDA Guidance - Control of Nitrosamine Impurities in Human Drugs
- FDA - Information about Nitrosamine Impurities in Medications
