Nitrosamine Impurities in Pharmaceuticals: Chemistry, Evolving Regulations and Strategic Risk Control

Nitrosamines are highly reactive, potentially DNA-damaging chemicals whose unexpected detection in June 2018 triggered worldwide recalls and intensified regulatory scrutiny. Following the recalls of several blood-pressure drugs, heart-burn remedies and antidiabetics, regulators in every major market made nitrosamine control a core element of Good Manufacturing Practice (GMP). Today, Marketing Authorization Holders (MAH) must identify all potential nitrosamine formation pathways, apply ultra-trace analytical methods, and implement robust risk-mitigation measures encompassing active ingredients, excipients, packaging, and finished products. Acceptable intakes (AI) are typically in the nanogram-per-day range and are adjusted as new scientific knowledge becomes available. Continuous vigilance and monitoring are therefore essential to ensure that medicines remain safe, effective, and fully compliant throughout their entire lifecycle.

This article provides manufacturers, quality leaders and regulatory affairs professionals, a concise overview of nitrosamine science, evolving regulations and the practical steps required to manage risk and maintain compliance.

1. What are nitrosamines and why do they matter?

In 2018, the discovery of N-nitrosodimethylamine (NDMA) in valsartan, a medication to treat hypertension, quickly followed by similar findings in ranitidine, metformin and rifampicin, exposed a structural weakness in pharmaceutical supply chains. Since then, the European Medicines Agency (EMA), the United States (US) Food and Drug Administration (FDA) and other regulators have issued specific guidance documents and strict timelines for the identification, assessment and control of nitrosamine impurities.

Nitrosamine formation can occur at almost any point in the lifecycle of a medicine and during manufacturing. The so-called “small nitrosamines” such as NDMA or N-Nitrosodiethylamine (NDEA) are created when trace amines in solvents, reagents or utilities react with nitrosating agents under the right chemical conditions. Larger nitrosamine drug-substance-related impurities (NDSRI), may be formed when an Active Pharmaceutical Ingredient (API) that already contains an amine group is itself nitrosated during synthesis, processing or storage. Excipients, nitrocellulose-based blister films, aluminum foils and even in vivo gastric chemistry can provide the nitrosating species that initiate the formation of either class of nitrosamines. As a result, virtually any oral dosage form that brings amines and nitrites into contact is potentially at risk.

2. Chemistry and formation pathways

All nitrosamines share the same reactive N-nitroso group in its structure (-N–N=O). This small structural motif renders the molecule electrophilic and prone to interacting with DNA. The figure below provides a simplified schematic of how nitrosation of a secondary amine can generate a nitrosamine.

In pharmaceutical operations, three situations can lead to the formation of nitrosamines:

1. Process inputs: Residual secondary or tertiary amines in raw materials, recycled solvents and cleaning agents can react with nitrites or other sources of nitrogen oxides, producing classic small nitrosamines.
2. Degradation: Drug substances that include vulnerable amine side chains may slowly transform into an NDSRI during long-term storage, especially in the presence of heat, moisture, or acidic micro-environments.
3. Packaging interaction: Certain blister laminates, coatings or inks based on nitrocellulose can release nitrosating agents that migrate and may drive nitrosamine formation.

Evaluating if one of these pathways is plausible for a given product is the first step towards effective control.

3. Patient-health impact and Acceptable Intakes

Once in systemic circulation, nitrosamines are rapidly metabolized, principally by hepatic cytochrome P450 enzymes, into short-lived intermediates that potentially alkylate DNA bases. Lesions that escape DNA-repair mechanisms may give rise to mutations that, over time, can lead to liver, gastric or other cancers.

To keep the lifetime excess cancer risk below 1 in 100 000, regulators set AI limits. For NDMA, the European Union (EU) and the US have aligned on an 18 nanograms per day limit, down from an initial 96 nanograms when the issue first emerged [1]. Today, agencies routinely publish compound-specific limits that distinguish between small nitrosamines and larger NDSRIs. When animal data are unavailable, companies must generate provisional limits through in silico methods or apply the Carcinogenic Potency Categorization Approach (CPCA). The CPCA assigns nitrosamines to one of five potency categories, with default AIs that range roughly from 18 nanograms per day for the most potent category to 1 500 nanograms per day for the least potent. These values are revised as new toxicological studies and modeling outputs emerge.

4. Evolving Global Framework for Nitrosamine Regulation

The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) M7 provides the primary framework for the control of mutagenic impurities, while ICH Q3A and Q3B address the qualification and control of impurities in drug substances and drug products. Building on this foundation, each region has issued additional nitrosamine-specific requirements.

In Europe, the EMA and the Coordination Group for Mutual Recognition and Decentralized Procedures-Humans (CMDh) have imposed a three-step action plan on companies.

• Step 1: Company-wide risk evaluations must be completed for all authorized medicines.
• Step 2: Confirmatory testing must be completed when a risk is identified in Step 1.
• Step 3: MAHs must file variations that document final control strategies and, where necessary, lower shelf-life specifications.

In the US, the FDA’s Center for Drug Evaluation and Research (CDER) has published a living series of guidance documents. The 2023 document on NDSRIs introduced a chemistry-based decision tree for limit setting and encouraged the use of read-across and in silico tools. A subsequent notice in August 2025 clarified expectations for nitrosamine formation originating in packaging materials such as infusion bags and elastomeric components. The agency updates its list of nitrosamine limits whenever new data becomes available, making it necessary for companies to maintain continuous monitoring and surveillance of these revisions.

In other regions, Health Canada, the UK’s Medicines and Healthcare products Regulatory Agency (MHRA), Japan’s Pharmaceuticals and Medical Devices Agency (PMDA) and the World Health Organization (WHO) have adopted numerical limits close to those of the EMA and FDA but maintain distinct reporting thresholds and grace periods. China’s National Medical Products Administration (NMPA) and India’s Central Drugs Standard Control Organization (CDSCO) have released interim notices that lean on ICH principles until full guidelines are published.

An ICH Nitrosamine Impurities Working Party is developing an M7 addendum that would standardize potency categories, analytical limits of quantification and dossier templates. Adoption is expected within the next few years, bringing greater global consistency but also higher documentation demands.

5. Nitrosamine risk-evaluation workflow

Effective control begins with the ICH Q9 philosophy of science- and risk-based quality management. Many companies start with a Failure Mode, Effects and Criticality Analysis (FMECA) to systematically map and rank every plausible nitrosamine-forming scenario by risk.

All steps that might co-locate an amine precursor and a nitrosating species, from raw-material reception to patient use, are listed and scored for severity, probability and detectability. The output is a ranked mapping that focuses resources on the highest-risk nodes.

If no credible formation pathway is identified, a documented rationale closes the assessment. Otherwise, the product enters analytical verification. Tier 1 is a limit test or broad screening able to show that each relevant nitrosamine is below 10 % of its AI. A successful Tier 1 result allows routine monitoring only, but if it fails, the company must perform fully quantitative analyses with a validated analytical method that achieves a limit of quantification at or below 10 % of the AI of the compound. Confirmed exceedances trigger corrective actions such as process optimization, reagent replacement, formulation shielding or packaging upgrades, followed by re-validation and notification to regulators.

6. Analytical strategy limits for laboratories

Achieving adequate sensitivity, often below ten parts per billion, is challenging for laboratories. High-resolution mass spectrometry or tandem mass spectrometry is often required for nitrosamines identification, and background artefacts may come from water, solvents and even laboratory tubing. Moreover, sourcing pure reference materials constitutes another challenge: custom synthesis of rare NDSRIs can take months and may yield standards that themselves contain trace NDMA or NDEA. Inter-laboratory studies and external quality schemes are therefore critical and necessary to demonstrate method robustness and reproducibility.

7. What’s next? Regulatory shifts and broader market impact

The next wave of regulatory changes will likely come on three fronts. First, machine-learning toxicology models built on expanding nitrosamine datasets will sharpen potency predictions, reducing reliance on lengthy animal studies, but obliging companies to manage computational workflows and data traceability. Second, the forthcoming revision of ICH M7 and the potential introduction of electronic risk-assessment templates will require MAHs to organize underlying data in a structured, machine-readable format that can be rapidly updated as new findings appear. Third, authorities have signaled that nitrosamine expectations may soon apply to combination products, homeopathic preparations, cosmetics and food supplements, sectors where guidance is still minimal. The 2025 U.S. FDA safety communication on nitrosamine contamination in plastic infusion bags, which are medical devices, underscores this extension beyond pharmaceuticals [2]. Manufacturers of healthcare products should therefore brace for new testing, modelling, and lifecycle-management duties. The inevitable increase in complexity can be handled efficiently only through a robust, forward-looking risk-management strategy.

Conclusion

Effective nitrosamine oversight is integral to modern GMP – and to sustaining public confidence in medicines and products across all life science sectors. A resilient control strategy must unite thorough risk assessment, ultra-sensitive analytics, data-driven toxicology and balanced process, formulation and packaging mitigation. With requirements evolving in real time, continuous horizon scanning and digital tools are indispensable.

Need assistance?

Efor’s multidisciplinary teams help clients navigate this demanding terrain. We provide end-to-end support that ranges from on-site FMECA workshops and analytical method development to dossier updates and GMP remediation, ensuring rapid compliance while safeguarding product supply and brand reputation.

To discuss your project, contact our expert teams within our Solution & Project Delivery at: solutionprojectdelivery@efor-group.com.

Resources:

[1] European Medicines Agency (EMA). “Questions and answers for marketing authorisation holders/applicants on the CHMP opinion for the Article 5(3) of Regulation (EC) No 726/2004 on nitrosamine impurities in human medicinal products.” EMA/409815/2020, Rev. 23 October 2025.

And U.S. Food and Drug Administration (FDA), Center for Drug Evaluation and Research (CDER). “Guidance for Industry: Control of Nitrosamine Impurities in Human Drugs.” Final Guidance, September 2024.

[2] U.S. Food and Drug Administration (FDA). « Emerging Scientific and Technical Information on Leachable NDBA and Other Small-Molecule Nitrosamines in Infusion Bags », August 2025.