Nitrosamines in Pharmaceuticals: Regulatory Requirements, Risk Assessment & Testing

Introduction

Nitrosamine impurities are a class of potentially carcinogenic impurities that can be present in pharmaceutical products or form during manufacturing, storage, or other stages of the product lifecycle.

The identification of nitrosamines such as N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) in medicines led global regulatory agencies to strengthen expectations for impurity risk assessment, analytical testing, root-cause investigation and mitigation.

Today, pharmaceutical manufacturers are expected to take a risk-based and science-driven approach to identify whether nitrosamines could form or be introduced into an active pharmaceutical ingredient (API), excipient, intermediate or finished drug product.

Regulatory expectations have also evolved beyond the originally identified small-molecule nitrosamines. Nitrosamine Drug Substance-Related Impurities (NDSRIs), which are structurally related to the API, are now an important part of regulatory risk assessment. FDA’s current guidance specifically distinguishes between small-molecule nitrosamines and NDSRIs and provides recommendations for risk assessment, testing and mitigation.

What Are Nitrosamine Impurities?

Nitrosamines are chemical compounds containing the characteristic N-nitroso functional group.

In pharmaceutical manufacturing, nitrosamines can potentially form when a nitrosatable amine comes into contact with a nitrosating agent under suitable chemical conditions.

A simplified representation is:

Amine + Nitrosating Agent → Nitrosamine

Nitrite-containing materials are particularly important because nitrite can generate nitrous acid under acidic conditions, which can participate in nitrosation reactions.

Potential formation may occur:

During API synthesis
During intermediate processing
During formulation
During drug-product manufacturing
During storage
Through interactions between API and excipients
Through degradation pathways
From contaminated raw materials
From certain processing aids or manufacturing inputs
Potentially from packaging-related sources

FDA specifically identifies nitrosation reactions involving amines and nitrite/nitrous acid as an important formation pathway. Packaging can also be a potential source of nitrosamines or nitrite-related materials.

Two Major Classes of Nitrosamine Impurities

1. Small-Molecule Nitrosamines

These nitrosamines are generally not structurally related to the API and may occur across different pharmaceutical products. Examples include:

NDMA – N-nitrosodimethylamine
NDEA – N-nitrosodiethylamine
NMBA – N-nitroso-N-methyl-4-aminobutyric acid
NDBA – N-nitrosodibutylamine
NMPA – N-nitroso-N-methylpiperazine
NPIP – N-nitrosopiperidine

The specific nitrosamine risk depends on the chemistry and manufacturing process associated with the product.

2. Nitrosamine Drug Substance-Related Impurities (NDSRIs)

NDSRIs are nitrosamine impurities that share structural characteristics with the API or API-related fragments.

They can form when a molecule containing a nitrosatable amine undergoes nitrosation.

NDSRIs can therefore be product-specific, meaning that the potential nitrosamine profile may differ substantially from one API to another.

FDA describes NDSRIs as a specific class of nitrosamines structurally related to the drug substance and generally unique to individual APIs.

Why Are Nitrosamines a Pharmaceutical Concern?

The major concern is their potential mutagenic and carcinogenic activity.

Certain nitrosamines can interact with biological systems to produce DNA-reactive metabolites, potentially causing genetic damage.

Long-term exposure to certain nitrosamines may therefore increase carcinogenic risk.

The regulatory approach is consequently based on controlling exposure to very low levels rather than treating nitrosamines like conventional pharmaceutical impurities.

This is why nitrosamine control involves both:

Hazard identification + Exposure assessment + Risk mitigation + Analytical verification

How Can Nitrosamines Enter or Form in Pharmaceutical Products?

Nitrosamine risk can originate from multiple sources.

API Manufacturing: Nitrosation can occur during chemical synthesis if nitrosatable amines and nitrosating agents are present under suitable conditions.

Raw Materials and Starting Materials: Impurities in starting materials, reagents, solvents or process chemicals may introduce nitrosamine precursors.

Excipients: Some excipients may contain trace nitrite or other components capable of contributing to nitrosamine formation.

Water and Processing Conditions: Process water and manufacturing conditions can influence the availability of nitrite and the chemical environment.

Drug-Product Manufacturing: Nitrosamines may form during granulation, coating, formulation or other manufacturing steps depending on the chemistry involved.

Storage: Formation can potentially continue during storage if the formulation contains the necessary precursors and environmental conditions favour the reaction.

Packaging: Packaging components may contribute nitrosamine-related substances or nitrite-related leachables under certain circumstances.

Pharmaceutical Nitrosamine Risk Assessment

Regulatory agencies expect manufacturers to conduct a risk assessment to determine whether nitrosamines could be present or form during the product lifecycle.

A robust risk assessment should consider the entire manufacturing process rather than focusing only on the finished product.

Step 1: Understand the API Structure

Identify whether the API or an intermediate contains:

Secondary amines
Tertiary amines capable of nitrosation
Other potentially nitrosatable functional groups

Damaged or improperly harvested crops may become more susceptible to fungal growth.

Step 2: Review Manufacturing Chemistry

Evaluate:

Reagents
Solvents
Catalysts
Acids and bases
Nitrite-containing materials
Process conditions
Reaction temperatures
pH
Purification steps

Step 3: Evaluate Excipients

Assess excipients for:

Nitrite content
Nitrosating potential
Supplier variability
Compatibility with the API

Step 4: Evaluate Drug-Product Formulation

Consider whether the formulation creates conditions that could promote nitrosamine formation.

Step 5: Evaluate Storage

Consider:

Temperature
Humidity
Shelf life
Packaging
Degradation pathways

Step 6: Determine Potential Nitrosamines

Based on the chemistry, identify specific nitrosamines that could potentially form.

Step 7: Establish an Analytical Strategy

Where a potential risk is identified, analytical testing should be performed using an appropriately sensitive and validated method.

Carcinogenic Potency Categorisation Approach (CPCA)

One of the important developments in nitrosamine regulation is the use of the Carcinogenic Potency Categorisation Approach (CPCA).

The CPCA uses structural characteristics to place certain nitrosamines into carcinogenic potency categories.

Each category is associated with a corresponding Acceptable Intake (AI).

FDA uses CPCA as one approach for establishing recommended AI limits for certain nitrosamine impurities, while compound-specific data or read-across may be used where appropriate.

The approach is particularly important for NDSRIs because compound-specific carcinogenicity data may not be available for every newly identified impurity.

What Is an Acceptable Intake (AI)?

An Acceptable Intake (AI) is the estimated daily amount of a nitrosamine impurity that is considered to pose no appreciable additional cancer risk under the applicable regulatory assessment. AI is generally expressed as:

ng/day (nanograms per day)

The corresponding concentration limit in a drug product depends on factors such as:

AI value
Maximum daily dose of the drug
Product formulation
Route of administration
Duration of treatment
Applicable regulatory framework

A simplified relationship is:

Concentration limit = Acceptable Intake ÷ Maximum Daily Dose

Therefore, the same nitrosamine may correspond to different concentration limits depending on the maximum daily dose of the medicinal product.

Current Regulatory Approach to Nitrosamine Limits

There is no single universal nitrosamine limit applicable to every pharmaceutical product.

The applicable AI depends on:

Specific nitrosamine
Carcinogenic potency
Available toxicological data
Regulatory jurisdiction
Product dose
Route of administration
Duration of exposure
Whether compound-specific data or read-across are available

FDA’s current nitrosamine information provides AI limits based on CPCA, compound-specific carcinogenicity/mutagenicity data and read-across approaches, along with certain interim AI limits.

FDA Requirements for Nitrosamine Control

The U.S. FDA’s Control of Nitrosamine Impurities in Human Drugs guidance recommends that manufacturers and applicants:

Conduct nitrosamine risk assessments
Identify potential sources and formation pathways
Perform confirmatory testing where a risk is identified
Establish appropriate controls
Implement mitigation strategies
Monitor nitrosamine levels where necessary
Submit appropriate regulatory changes

FDA’s September 2024 revised guidance distinguishes between small-molecule nitrosamines and NDSRIs and provides recommendations covering risk assessment, testing and mitigation.

FDA also maintains a continuously updated page containing recommended AI limits and related technical information. The page was updated in August 2026, demonstrating that nitrosamine regulatory expectations continue to evolve.

EMA Requirements for Nitrosamine Management

The European Medicines Agency (EMA) requires marketing authorisation holders and applicants to assess and control the risk of nitrosamine impurities in human medicinal products.

The EMA framework addresses:

Nitrosamine risk assessment
Identification of potential nitrosamines
Acceptable intake limits
Confirmatory testing
Risk mitigation
Regulatory submissions
New and existing medicinal products

The EMA Q&A framework incorporates approaches including:

Carcinogenic Potency Categorisation Approach (CPCA)
Read-across
Enhanced Ames Test (EAT)
Other appropriate toxicological approaches

EMA’s current Q&A document was updated in October 2025, while its acceptable-intake appendix was updated in June 2026.

Nitrosamine Risk Assessment in India

For pharmaceutical products manufactured or marketed in India, manufacturers should consider applicable CDSCO requirements, Indian pharmacopoeial requirements where relevant, and expectations arising from internationally recognised pharmaceutical quality and impurity-control frameworks.

CDSCO’s public notices include specific regulatory attention to the safety of ranitidine products associated with NDMA impurity, reflecting the broader regulatory importance of nitrosamine control in India.

For products intended for export, manufacturers should additionally evaluate the requirements of the destination market, particularly where FDA or EMA expectations apply.

Analytical Testing of Nitrosamines

Nitrosamines are typically present at very low concentrations, making analytical sensitivity critical.

Testing methods should be capable of detecting and quantifying the relevant nitrosamine at concentrations sufficiently below the applicable regulatory limit.

Common analytical technologies include:

LC-MS/MS

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) is widely used for sensitive and selective analysis of nitrosamines. It can be particularly useful for:

Polar nitrosamines
Thermally sensitive compounds
Multi-analyte methods
Complex pharmaceutical matrices

GC-MS/MS

Gas Chromatography-Tandem Mass Spectrometry (GC-MS/MS) can be suitable for volatile or semi-volatile nitrosamines. The appropriate technique depends on:

Target analytes
API or drug-product matrix
Required LOQ
Chemical properties
Sample preparation
Regulatory requirement

Analytical Method Requirements

Nitrosamine methods require careful development and validation because the target concentrations can be extremely low. Important characteristics include:

Specificity
Selectivity
Sensitivity
Accuracy
Precision
Linearity
Recovery
Limit of Detection (LOD)
Limit of Quantification (LOQ)
Matrix effects
Stability
Carryover
Measurement uncertainty

The analytical LOQ should be appropriate for the applicable AI-derived concentration limit.

A method that cannot reliably quantify below the required regulatory threshold may not be suitable for demonstrating compliance.

Confirmatory Testing vs Screening

A risk assessment should determine whether testing is necessary and which analytical approach is appropriate.

Screening May be used during development or investigation to determine whether a potential nitrosamine is present.

Confirmatory Testing Where a nitrosamine risk is identified, confirmatory testing using a validated analytical method is generally expected.

FDA specifically recommends confirmatory testing when a nitrosamine risk is identified.

Forced Degradation and Nitrosamine Formation Studies

For NDSRIs, understanding whether a nitrosamine can actually form from the API may require additional scientific investigation. Studies may evaluate:

Nitrosating conditions
API degradation
Excipients
Storage conditions
Formulation interactions
Process conditions

Forced degradation or targeted formation studies can help determine whether a theoretically identified nitrosamine is chemically plausible under relevant conditions.

FDA’s current implementation information specifically discusses assessment of whether NDSRIs can form under targeted forced-degradation conditions.

Enhanced Ames Test for Nitrosamines

The Enhanced Ames Test (EAT) is an important toxicological tool in the assessment of certain nitrosamines.

It is designed to improve the sensitivity of bacterial reverse mutation testing for nitrosamine-related mutagenic hazards.

Both FDA and EMA have incorporated enhanced Ames testing approaches into their evolving nitrosamine frameworks.

However, analytical testing and toxicological testing serve different purposes:

Analytical testing determines how much nitrosamine is present.

Toxicological testing helps assess the hazard and support the safety assessment.

Nitrosamine Control Strategy

Testing alone is not sufficient for long-term nitrosamine control.

A comprehensive control strategy may include:

1. Raw Material Control

Evaluate starting materials, reagents, solvents and excipients.

2. Process Control

Control process conditions that could promote nitrosation.

3. Supplier Qualification

Assess supplier controls and variability in nitrite-containing materials.

4. Formulation Control

Evaluate API–excipient interactions and formulation conditions.

5. Packaging Assessment

Perform appropriate testing based on identified risk.

6. Analytical Monitoring

Consider potential contribution from packaging materials where scientifically relevant.

7. Stability Monitoring

Evaluate whether nitrosamine levels can increase during storage.

8. Change Control

Reassess nitrosamine risk following changes to:

API supplier
Excipient supplier
Manufacturing process
Formulation
Packaging
Manufacturing site
Storage conditions

Why Nitrosamine Testing Is Important for Pharmaceutical Manufacturers

Nitrosamine testing can support:

API qualification
Excipient qualification
Drug-product development
Process validation
Batch release assessment
Stability studies
Regulatory submissions
Supplier qualification
Root-cause investigations
Export compliance
Post-market monitoring

Testing frequency should be determined through a documented risk assessment, rather than automatically applying the same testing frequency to every batch and product.

Common Nitrosamines Tested in Pharmaceuticals

Depending on the product-specific risk assessment, testing may include:

NDMA
NDEA
NMBA
NDBA
NMPA
NPIP
N-nitroso compounds specific to the API
Other identified NDSRIs

The analytical panel should not be selected solely from a generic list.

It should be based on the chemistry and manufacturing pathway of the specific API and drug product.

Key Challenges in Nitrosamine Testing

Extremely Low Regulatory Limits

Nitrosamine AI values can be in the nanogram-per-day range, requiring highly sensitive analytical methods.

Complex Matrices

Drug products may contain multiple excipients that can interfere with extraction or detection.

Trace-Level Contamination

Background contamination, laboratory materials and analytical carryover can become significant at ultra-low concentrations.

Matrix Effects

Ion suppression or enhancement can affect LC-MS/MS quantification.

Multiple Potential Nitrosamines

One API may have more than one potential nitrosation site.

Changing Regulatory Expectations

AI values, analytical approaches and regulatory expectations continue to evolve as new scientific information becomes available.

The ICH has also identified nitrosamine control as an area requiring further harmonisation, including work on acceptable-intake approaches, enhanced Ames testing, multiple nitrosamines and less-than-lifetime exposure considerations.

How Eureka Supports Nitrosamine Testing

Eureka can support pharmaceutical manufacturers and API/product developers with analytical testing and risk-based impurity assessment for nitrosamines.

Testing Support

Depending on the product and analytical requirement, testing can be designed for:

Pharmaceutical Matrices

Testing may be relevant for:

APIs
Finished pharmaceutical products
Tablets
Capsules
Oral solid dosage forms
Liquid formulations
In-process materials
Selected raw materials and excipients

Compliance Applications

Eureka can support:

Nitrosamine risk assessment programmes
Method development and validation support
Confirmatory testing
Batch assessment
Stability testing
Supplier qualification
Investigation of unexpected nitrosamine results
Regulatory compliance testing
Export-market requirements

The appropriate analyte panel, method and acceptance criteria should be established according to the specific API, formulation, dose, regulatory jurisdiction and intended application.

Practical Nitrosamine Risk Assessment Workflow

A practical pharmaceutical nitrosamine programme can follow this sequence:

API & Process Review
↓
Identify Nitrosatable Amines & Nitrosating Sources
↓
Evaluate API, Excipients & Manufacturing Conditions
↓
Identify Potential Nitrosamines / NDSRIs
↓
Perform Toxicological & Regulatory Assessment
↓
Establish Applicable AI
↓
Develop Sensitive Analytical Method
↓
Perform Confirmatory Testing
↓
Compare Exposure With Applicable AI
↓
Implement Mitigation & Control Strategy
↓
Monitor Through Stability / Lifecycle Management

Key Takeaways

Nitrosamines are potentially carcinogenic impurities that require specific risk management in pharmaceutical products.
Two important categories are small-molecule nitrosamines and NDSRIs.
Nitrosamines may originate from API synthesis, intermediates, excipients, manufacturing processes, degradation or packaging-related sources.
Risk assessment should consider the entire product lifecycle, not only the finished product.
Acceptable Intake limits are generally expressed in ng/day and depend on the specific nitrosamine and applicable regulatory assessment.
FDA uses approaches including CPCA, compound-specific data and read-across for establishing recommended AI limits.
EMA also uses CPCA, read-across and enhanced toxicological approaches within its nitrosamine framework.
LC-MS/MS and GC-MS/MS are important analytical platforms for trace-level nitrosamine testing.
Analytical methods must demonstrate appropriate sensitivity, specificity, accuracy, precision and LOQ.
Testing should be supported by root-cause analysis and preventive controls, not treated as the only mitigation measure.
Nitrosamine regulatory expectations continue to evolve, making periodic review of current regulatory requirements essential.

Frequently Asked Questions (FAQ)

1. What are nitrosamines in pharmaceuticals?

Nitrosamines are a group of chemical impurities that may form during pharmaceutical manufacturing, formulation or storage and that can have mutagenic and carcinogenic potential.

2. What are NDSRIs?

NDSRIs are Nitrosamine Drug Substance-Related Impurities that are structurally related to the API and may form through nitrosation of the drug substance or API-related fragments.

3. What are the most commonly tested nitrosamines?

Commonly evaluated compounds include NDMA, NDEA, NMBA, NDBA, NMPA and NPIP, along with API-specific NDSRIs where applicable.

4. What is the acceptable limit for NDMA?

There is no single concentration limit applicable to every pharmaceutical product. The applicable AI and corresponding concentration limit depend on the regulatory jurisdiction, product dose and current regulatory assessment.

5. What is the FDA approach to nitrosamine impurities?

FDA recommends risk assessment, confirmatory testing where a risk is identified, mitigation and control strategies. Its current framework includes AI limits based on CPCA, compound-specific data and read-across approaches.

6. What is the EMA approach to nitrosamines?

EMA requires marketing authorisation holders and applicants to assess, test and control nitrosamine impurities. Its framework includes CPCA, acceptable-intake limits, read-across and enhanced Ames testing approaches.

7. Which instruments are used for nitrosamine testing?

LC-MS/MS and GC-MS/MS are commonly used depending on the chemical properties of the target nitrosamine and the pharmaceutical matrix.

8. Is nitrosamine testing mandatory for every pharmaceutical product?

Not necessarily. The need for testing should be determined through a product-specific nitrosamine risk assessment. Where a potential risk is identified, appropriate confirmatory testing may be required.

9. Can NDSRIs form during storage?

Yes. If the necessary precursors and chemical conditions are present, nitrosamine formation can potentially occur during storage. Stability and formulation conditions should therefore be considered in the risk assessment.

10. Can Eureka support nitrosamine testing?

Yes. Eureka can support pharmaceutical manufacturers with nitrosamine analytical testing and related impurity-control programmes, subject to the applicable analytical scope, matrix and method requirements.

Official References

FDA – Control of Nitrosamine Impurities in Human Drugs, Guidance for Industry
FDA – Recommended Acceptable Intake Limits for Nitrosamine Drug Substance-Related Impurities
FDA – CDER Nitrosamine Impurity Acceptable Intake Limits
EMA – Nitrosamine Impurities: Guidance for Marketing Authorisation Holders
EMA – Questions and Answers on Nitrosamine Impurities in Human Medicinal Products
EMA – Appendix 1: Acceptable Intakes Established for N-Nitrosamines
EMA – Appendix 2: Carcinogenic Potency Categorisation Approach for N-Nitrosamines
EMA – Appendix 3: Enhanced Ames Test Conditions for N-Nitrosamines
ICH M7(R2) – Assessment and Control of DNA Reactive (Mutagenic) Impurities in Pharmaceuticals to Limit Potential Carcinogenic Risk
CDSCO – Applicable Pharmaceutical Quality and Impurity-Control Requirements
United States Pharmacopeia – Applicable Nitrosamine/Impurity Testing Chapters and Standards
European Pharmacopoeia – Applicable Pharmaceutical Impurity Requirements

Conclusion

Nitrosamine control has become an important component of modern pharmaceutical quality management.

The challenge is not simply to test for NDMA or NDEA, but to understand whether a pharmaceutical product has the chemical potential to generate nitrosamines, identify the specific impurities that could form, determine the applicable acceptable intake, and establish a scientifically justified control strategy.

A comprehensive programme therefore combines:

Risk Assessment + Process Understanding + Toxicological Assessment + Sensitive Analytical Testing + Root-Cause Investigation + Risk Mitigation

For pharmaceutical manufacturers, API suppliers and drug-product developers, proactive nitrosamine assessment can help identify potential risks earlier, support regulatory compliance and strengthen the overall quality and safety of medicinal products.