N-nitrosamine Impurities in Pharmaceuticals. Three-Step Control Under ICH M7, SP RF XV and EAEU Rules
A batch of valsartan has been manufactured, packaged, and is ready for shipment. Then the quality control result arrives — N-nitrosodimethylamine (NDMA), a substance on the World Health Organization’s list of probable human carcinogens, has been detected in the tablets. The batch is sent for destruction, pharmacies receive recall notices, and the regulator asks: how did this get into the finished product?
This exact situation unfolded in 2018 when a Chinese manufacturer of the valsartan active pharmaceutical ingredient (API) discovered NDMA and N-nitrosodiethylamine (NDEA) in its products. The recall spanned dozens of countries. The European Medicines Agency (EMA), the US Food and Drug Administration (FDA), and other regulators launched inspections of the entire sartan class, then expanded the scope to ranitidine, metformin, and other drugs. It became clear: the problem was hidden but systemic.
Seven years have passed since then. The State Pharmacopoeia of the Russian Federation, 15th Edition (SP RF XV), included a dedicated General Pharmacopoeia Monograph on nitrosamines, and the requirements of ICH M7 have been integrated into the Eurasian Economic Union (EAEU) regulatory framework. This article breaks down how the entire system works: where nitrosamines come from, how they are detected, and what to do with the results.
Why Nitrosamines Appeared Everywhere
Before the valsartan crisis, nitrosamines were rarely discussed in the pharmaceutical industry. Organic synthesis impurities, residual solvents, and heavy metals were well-known concerns. Nitrosamines, however, were considered a problem for the food industry and tobacco products — not for tablets.
The mistake lay in the chemistry of manufacturing itself. Nitrosamines form through the interaction of secondary amines with nitrosating agents: nitrites, nitrogen oxides, and residual synthesis reagents. These conditions occur at various stages of medicinal product manufacturing far more frequently than previously assumed. The investigation into the sartan crisis identified five main pathways for nitrosamines to enter a drug:
1. Active Pharmaceutical Ingredient Synthesis. If the process uses secondary amines or ammonium salts together with nitrosating agents under acidic conditions, the nitrosation reaction is practically unavoidable. In the valsartan case, the source was dimethylformamide (DMF) — a solvent that contained dimethylamine as a decomposition impurity.
2. Excipients. Lactose, starch, and microcrystalline cellulose may contain trace amounts of nitrites. Upon contact with the amino groups of the API directly within the tablet, nitrosamine drug substance-related impurities (NDSRIs) are formed.
3. Primary Packaging. The nitrocellulose coating on aluminum foil in blister packs can react with the amines of the drug during storage.
4. Recovered Solvents and Shared Equipment. When the same manufacturing equipment is used to synthesize different substances and solvents are recycled without sufficient purification, contamination transfers from batch to batch.
5. Water and Air in Production Areas. Technical water containing nitrites and airborne contamination are less significant but real sources.
This means that nitrosamines are potentially present in any drug with a chemically synthesized API — not necessarily at dangerous concentrations, but every product must be evaluated.
How Regulation Has Changed
ICH M7(R2): New Limits for Nitrosamines
The ICH M7 guidance «Assessment and Control of DNA Reactive (Mutagenic) Impurities in Pharmaceuticals to Limit Potential Carcinogenic Risk» predated 2018, but the sartan crisis made nitrosamines a primary regulatory focus. Version R2 added an addendum with individual acceptable intake (AI) values for specific compounds.
Why does this matter? Previously, a general threshold of toxicological concern (TTC) of 1.5 µg/day was applied to mutagenic impurities. This approach worked for most impurities. Nitrosamines, however, belong to the Cohort of Concern, a group where the general TTC is inapplicable because their carcinogenic potency is too high even at extremely low doses.
AI values established by ICH M7(R2):
| Compound | AI, ng/day |
|---|---|
| N-nitrosodimethylamine (NDMA) | 96 |
| N-nitrosodiethylamine (NDEA) | 26.5 |
| N-nitroso-N-methyl-4-aminobutyric acid (NMBA) | 96 |
| N-nitrosodipropylamine (NDPA) | 26.5 |
| 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) | 100 |
For comparison: typical organic synthesis impurities are controlled at the microgram level. For nitrosamines, the limits are in nanograms — hundreds of times stricter.
SP RF XV: General Pharmacopoeia Monograph OFS 1.2.2.2.0031
SP RF XV included General Pharmacopoeia Monograph OFS 1.2.2.2.0031 «Determination of N-nitrosamine impurities,» approved by Order of the Ministry of Health of Russia No. 377 dated July 20, 2023. The monograph establishes requirements for analytical control methods and principles for selecting a method based on the type of impurity and the drug matrix.
The monograph aligns with international requirements while accounting for the technical capabilities of Russian laboratories and the specific drug nomenclature on the Russian market. If a company operates in Russia, its nitrosamine control method must comply with OFS 1.2.2.2.0031.
EAEU: Nitrosamines Through the Registration Rules
At the EAEU level, there is currently no separate decision dedicated exclusively to nitrosamines. Requirements are built into the general regulatory framework: the Rules of Registration and Examination of Medicinal Products (Decision of the Council of the Eurasian Economic Commission (EEC) No. 78 dated November 3, 2016) require dossier compliance with international ICH guidelines, including M7. The EAEU Pharmacopoeia, established by EEC Collegium Decision No. 100 dated August 11, 2020, provides the analytical basis for impurity control methods.
In practice, nitrosamine risk assessment for EAEU registration follows the same logic as EMA or FDA procedures: risk evaluation, confirmatory testing, and risk management. National authorized bodies in member states may issue their own methodological documents with additional detail for local dossiers.
CPCA: Categorization Without Experimental Data
What about nitrosamines for which no carcinogenicity data exist at all? In 2023, EMA and FDA introduced the Carcinogenic Potency Categorisation Approach (CPCA) — a method for assigning carcinogenic potential categories to NDSRIs. Long-term animal studies have simply not been conducted for most impurities derived from active substances, and waiting two years for results is not feasible.
CPCA assigns a risk category to an impurity based on its molecular structure. The more hydrogen atoms at the carbon adjacent to the nitroso group and the fewer deactivating groups present, the higher the carcinogenic potential and the stricter the AI limit.
CPCA categories (EMA Appendix 2, EMA/451665/2023):
| Category | AI, ng/day | EMA Example |
|---|---|---|
| 1 | 18 | N-nitrosolorcaserin |
| 2 | 100 | N-nitrososertraline |
| 3 | 400 | Nitrosopiperazines (aripiprazole) |
| 4 | 1500 | N-nitrosomoxifloxacin |
| 5 | 1500 | N-nitrosofelodipine |
If structural analysis under CPCA yields a strict limit, the manufacturer may conduct an Enhanced Ames Test (EAT). A negative result in a validated EAT allows the impurity to be controlled at 1500 ng/day as non-mutagenic.
NDSRIs: The Next Level of Complexity
If NDMA and NDEA were the initial warning signs in 2018, by 2023-2025 regulators shifted focus to NDSRIs. Every drug potentially produces a unique impurity with a unique structure — which is a more complex challenge than controlling a standard list of ten compounds.
The formation mechanism is straightforward: if an API contains a secondary amino group (common in many drugs for hypertension, diabetes, and psychiatric conditions), it can react with nitrites from excipients directly within the tablet during storage. The reaction rate depends on humidity, temperature, and pH of the dosage form.
According to the 2024 guidance from the Scientific Centre for Expert Evaluation of Medicinal Products (NTSESMP) of the Ministry of Health of the Russian Federation, NDSRI risk assessment requires not only an analysis of the manufacturing process but also a study of the API degradation profile: during storage, an amino group may be liberated from the molecular structure and become even more reactive. Checking only the known ICH nitrosamines (NDMA, NDEA, NMBA, and a few others) is not sufficient. A structural analysis of the API for potential NDSRIs is needed, with AI calculation via CPCA or experimental confirmation. For drugs with piperazine or morpholine-type amines, this is particularly relevant.
The Three-Step Approach in Practice
International requirements and Russian legislation describe a unified algorithm for working with nitrosamines: the three-step approach (Step 1, Step 2, Step 3).
Step 1. Risk Evaluation
The manufacturer analyzes the entire manufacturing process: API synthesis, finished dosage form composition, packaging type, and storage conditions. The goal is to identify whether chemical prerequisites for nitrosamine formation exist. Laboratory testing is not required at this stage — a documented evaluation is sufficient.
If no risk is identified, the report is retained by the manufacturer and provided to the regulator upon request. If a risk is identified, proceeding to Step 2 is mandatory.
Step 2. Confirmatory Testing
This step involves actual analysis of drug samples. The technical challenge here is that impurities must be detected at levels below 0.1 ppm. Conventional HPLC with UV detection is not suitable — it lacks the sensitivity and selectivity needed when a high-concentration API is present.
Practical analytical methods for Step 2 — mass spectrometry:
| Method | Application | Key Characteristics |
|---|---|---|
| HPLC-MS/MS | NDSRIs and non-volatile nitrosamines | High selectivity; complex sample preparation |
| GC-MS/MS | Volatile NDMA, NDEA | Excellent sensitivity; risk of artifact formation at elevated temperature |
The limit of quantitation (LOQ), per ICH Q2(R2), must not exceed 10-30% of the established AI limit.
Step 3. Risk Management
A nitrosamine has been detected — what next? The manufacturer compares the detected level against the AI limit:
- Below 10% of AI: routine batch-by-batch control is not required; periodic monitoring is sufficient.
- 10-100% of AI: a specification entry and control of every released batch are required.
- Above 100% of AI: the batch cannot be released for distribution.
If levels are consistently elevated, the manufacturing process is revised: secondary amines are replaced with primary ones, nitrosation inhibitors (ascorbic acid, α-tocopherol) are added, nitrite specifications for excipients are tightened, or packaging is switched to a non-nitrocellulose alternative.
Action Plan
A concrete checklist for quality or regulatory affairs professionals.
1. Inventory your portfolio. Categorize products: biologics (generally lower nitrosamine risk), synthetic small molecules (mandatory risk evaluation), and products with amino-containing APIs (highest priority). Every synthetic product requires a documented Step 1 report.
2. Review Step 1 documentation. Risk evaluation is not a formality. During an inspection, regulators examine the completeness of the chemical analysis: are all synthesis stages covered? Are excipients and packaging type accounted for? A superficial report means Step 2 under pressure.
3. Confirm analytical method availability. For products with identified risk, a validated mass spectrometric method is required. Verify with your laboratory: is HPLC-MS/MS or GC-MS/MS equipment available? Has the method been validated per ICH Q2(R2)? Does the LOQ meet requirements for the specific nitrosamine?
4. Update the registration dossier if necessary. If Steps 1-2 reveal nitrosamine content above 10% of the AI, the specification must include control of that impurity. The variation is submitted under the applicable procedure — EAEU or national.
5. Track limit updates. The list of nitrosamines and their AI values continues to expand: ICH, EMA, and FDA publish updates regularly. For Russia and the EAEU, monitor current NTSESMP guidance and EEC decisions at eurasiancommission.org and roszdravnadzor.gov.ru.
By 2025, nitrosamines are no longer a surprise. The three-step control system is already embedded in the practice of leading companies: risk evaluation, mass spectrometric analysis, management against AI thresholds. Those who have delayed this work face growing regulatory pressure — from SP RF XV, EAEU registration requirements, and an increasingly active inspection environment — all moving in the same direction.
Regulatory Framework:
1. General Pharmacopoeia Monograph OFS 1.2.2.2.0031 «Determination of N-nitrosamine impurities,» State Pharmacopoeia of the Russian Federation, 15th Edition (approved by Order of the Ministry of Health of Russia No. 377 dated July 20, 2023)
2. Decision of the Council of the EEC dated November 3, 2016, No. 78 «Rules of Registration and Examination of Medicinal Products for Medical Use» (as amended through 2025)
3. Decision of the Collegium of the EEC No. 100 dated August 11, 2020 «On the Pharmacopoeia of the Eurasian Economic Union»
4. ICH M7(R2) «Assessment and Control of DNA Reactive (Mutagenic) Impurities in Pharmaceuticals»
5. EMA/409815/2020 Rev.23, Appendix 2 EMA/451665/2023 «Nitrosamines Q&A: Carcinogenic Potency Categorisation Approach»
6. ICH Q2(R2) «Validation of Analytical Procedures»
7. NTSESMP Guidance on nitrosamine risk assessment (2024)