Nitrosamines, such as N-nitrosodimethylamine (NDMA), are probable human carcinogens that pose significant health risks, including the potential for liver, stomach, and esophageal cancers. Nitrosamine Drug Substance Related Impurities (NDSRIs) are also of concern due to their potential genotoxicity. Regulatory agencies are now well aware of the potential safety risks and have issued guidance and set stringent limits on acceptable nitrosamine levels in pharmaceutical products.
Nitrosamine impurities can form via nitrosation (a chemical reaction involving the transfer of a NO group from a nitrous acid-derived compound to a nucleophile) of amines (secondary, tertiary and quaternary) reacting with nitrous acid, often produced by acidification of nitrites. The resulting impurities fall into two general structural classes: small- molecule “free” nitrosamine impurities, which do not share structural similarity with the API and are found in many different drug products, and Nitrosamine Drug Substance Related Impurities (NDSRIs) that are structurally similar to, and generally unique to, each API.
Unlike small-molecule N-Nitrosamine impurities, which can be formed during manufacturing processes, NDSRIs are predominantly formed during the formulation and storage of pharmaceutical products, specifically with APIs containing secondary and tertiary amines. They form when the APIs react with residual nitrites in excipients, including water.
NDSRI formation can be triggered by part per-million levels of nitrite impurities (such as those found in commonly used excipients), so many amine-containing drug products are now known to be at risk of nitrosamine formation. NDSRIs are a specific challenge for both manufacturers and regulators as they are unique to each drug and can be difficult to predict. Their presence above acceptable limits can compromise a drug’s safety and quality and, some cases, may lead to product recalls.
The pharmaceutical industry is developing mitigation strategies to reduce NDSRI formation. For small-molecule nitrosamine formation, using antioxidants such as ascorbic acid or alpha-tocopherol as inhibitors, or increasing the pH of the formulation by incorporating excipients such as sodium carbonate have been successful strategies, in addition to checking and controlling nitrites in raw materials. These may also be successful strategies for reducing NDSRI formation, but of course have to be confirmed for each specific API and manufacturing process.
In parallel to the industry working to mitigate risks, regulatory strategies and guidance have been evolving.
In August 2023, the FDA issued a final guidance on the daily Acceptable Intake (AI) limits for any given NDSRI based on predicted carcinogenic potency categorization (1). This was followed by an updated final guidance on “Control of Nitrosamine Impurities in Human Drugs in September 2024 (2).
There is a looming deadline of August 1, 2025 by which date, manufacturers must ensure that all NDSRIs in their products adhere to these newly established AI limits. Urgent action is therefore essential to comply and avoid potential regulatory consequences.
Low limits of NDSRIs require sensitive, specific and accurate analytical methods. At BioPharmaSpec, we rely on cutting-edge analytical techniques to ensure our nitrosamine testing delivers precise, consistent and reproducible results.
Our suite of instruments includes highly sensitive mass spectrometers that will detect nitrosamines at trace levels:
Such analytical tools provide the experts at BioPharmaSpec the ability to design and execute sensitive screening methods for NDSRIs as well as developing quantitative assessment methods even in the most complex DPs. Structural investigation, elucidation and confirmation of NDSRIs are also important aspects of the testing portfolio.
With regulatory agencies like the US FDA and The European Medicines Agency (EMA) setting stringent limits on acceptable nitrosamine levels in pharmaceutical products, it is crucial to ensure your drug formulations meet safety standards and protect patient health.
Whether you want to screen for potential NDSRIs in your DS or DP, establish methods for quantitation of even the most complex NDSRIs or develop a routine testing method, contact us today to find out how you can quickly start using LC-MS(MS) and other techniques to give you confidence in your nitrosamine control strategies.
