⚖️ Risk assessment not strong enough, specifically on related impurities containing secondary amine

Hello, have you ever been challenged by any health authorities when submitting a registration file, specifically about secondary amine presents on specified impurity, which would not have been sufficiently assessed, or considering that the risk assessment was not sufficiently strong?

1 Like

A nitrosamine risk assessment should consider ANY vulnerable amine for the potential formation of the impurity. Of course, all the chemistry, reactivity, and safety conditions will determine the level of risk, if any. But amine sources cannot be ignored or excluded.
I see a higher frequency of this when risk assessments are tasked solely to the Reg Affairs teams. It’s a continuous reminder that a declaration letter saying ‘free of Nitrosamines’ is not enough evidence of no risk.

I would like to post a simple question here for our community. What would you have done differently if you had to redo all the risk assessment work using the knowledge and experience you gained in all these 4 years?

Thoughts! @AndyTeasdale @schlinjo1975 @David @conudel @Yosukemino @Diego_HM @mflorea @Pradpharma @IreneNS @lucas10mauriz @Frabaneda @jason.brown @Ulrich @AndresJ @paliog


To the question asked, I agree. Everything should be evaluated. However, I think you will reach a dead end very quickly. Ideally, the impurity does not form a stable nitrosamine. Good luck procuring a suitable reference standard. You will likely need to make one yourself. Given the low levels of impurities that are permitted, the odds of it forming a meaningful amount are slim, but how do you write that up? I would hope that the structure is similar enough to the API to be able to presume a similar speed of reaction. In which case, one could solve for the expected formation over time given the impurity limit.

To the question from @Naiffer_Host, there are two things I would do differently.

  1. Define the core team in the organization. Working with them, define the full process and responsibilities. I keep seeing teams where individuals only understand their parts, at best. This continually leads to pauses in the work, where people are asking what next?

  2. Simply define the risk assessment as a FMEA or similarly structured risk assessment based on surveys, process, etc. along with a memo noting the findings and next steps. It seems that many are overcomplicating this.


I concede with @jason.brown thoughts.

Impurities could be small sized or large complex API based. Whatever be the case, we may need to borrow the science and strategy from all multidisciplinary teams and address it. Definitely experience gained throughout this journey would help.

At this point of time, i guess impurities (secondary amine) derived nitrosamines might not reach a scale where their exposure could really cause mutagenicity driven cancer.

Nevertheless- seeing the above case raised by @Beltran - It looks now we may need to be careful when we use the statement “free of Nitrosamines”.

1 Like

Thanks already for the interesting feedback.

Always challenging to consider the '“no risk” based on the level to be present, in link with the AL to be considered, if a high dose product, AL could be quite low. What is the limiting factor in term of formation of the nitrosamine, the quantity of nitrite, or the level of the amine? in this interesting publication Redirecting, it appears that even 0,1% of impurity could lead to certains content of nitrosamine.

In our publication from last year, we assessed vulnerable amines in APIs and all the related impurities. We estimated about 2200 impurities structures contained in USP-NF have vulnerable amines (720 secondary, 1493 tertiary).


@Naiffer_Host @Beltran
We were continuously adjusting to the state of the art, changing guidelines, lessons learned from deficiencies raised by health authorities, as we kept accumulating experience. We are doing it differently then couple of years ago, but we all are still on a learning curve, including the reviewers of the agencies. Our strategy shifted to doing more than necessary rather than less confirmatory testing, then gradually stabilized at a rational level. The risk assessments are also going deeper, this may be eventually time saving.
Secondary amine impurities would be certainly flagged by health authorities if the API itself is not a secondary amine of similar reactivity, or cannot justify the absence of potential nitrosamine contamination by calculations based on maximum nitrite level in the formulation or other mechanisms. Probably, potential secondary amine impurities of impurities would be also flagged, for ex. dimethyl amine in dimethylformamide residual solvent. Therefore, it is better to specify and assess the possibility of its occurrence, and if it is the case, demonstrate by documented calculations that the risk is negligible compared to the AI.


Absolutely correct, Naiffer. Merely stating ‘free of Nitrosamines’ in a declaration letter is not sufficient evidence of no risk.

In my opinion, a comprehensive Nitrosamine Impurity assessment should be conducted by R&D/MS&T/Process scientists rather than regulatory personnel. However, health authority guidance and updates should be provided by regulatory and quality personnel. Furthermore, if there are updates in the guidance, a reassessment of affected products should be performed to redefine the limit, considering worst-case scenarios.


In my opinion, the issue of nitrosamines (NDSRI) related to impurities may be generally summarized in two main cases:

  • API is a secondary amine (e.g. Fluoxetine) >> known NDSRI (e.g. N-nitroso Fluoxetine)
    one or more impurities are secondary amines related to the API (e.g. Impurities A, B and C of Fluoxetine)
    In this case, all secondary amines (API + imp.A,B,C) may be nitrosated, but the dominant NDSRI will be N-nitroso Fluoxetine. The amounts of the theoretical N-nitroso impurities should be negligible.

  • API is a tertiary amine (e.g. dimethylamino-something), but one impurity (e.g. desmethyl-API) may form a nitrosamine (e.g. N-nitrosodesmethyl-API).
    In this case all the nitrite present in the formulation will react with the impurity, not with the API (in some cases an oxidative dealkilation of API may occur, but this is a more complex case).
    Therefore in this case the NDSRI related to the impurity will be the one (or the main) nitrosamine and its amount will not be negligible.


I agree with @Naiffer_Host and @jason.brown. Companies should consider cases of secondary and tertiary amines along with any sources of nitrosating agents that could react with the amine to form nitrosamine. Then the question moves to “is the nitrosamine stable”. Then is the nitrosamine genotoxic. There could be other follow-up items to consider such as what are the ways that a company could reduce nitrosamine formation for this secondary amine. I would love to see a benchmarking conversation on the topic of what is sufficient in a risk assessment, and what have companies seen. Of course, only non-proprietary information could be shared or situations have to be phrased to remove specifics. However, I think a benchmarking session is the best way to generate ideas and develop best practices based on real world experiences. Also, are companies leaving the nitrosamine assessment generation as the responsibility of one person or a cross functional team? There are lots of questions that companies still have and sharing questions and experiences in a friendly, non-judgmental session can allow for aligned and consistent practices across industry. I would love it if USP could convene such an event.


@Naiffer_Host In my perspective, two key words come to mind: collaboration and updating.

I’d like to emphasize the importance of fostering collaboration and promoting information sharing among regulatory authorities, pharmaceutical companies, and analytical laboratories. Such collaboration is essential to facilitate the exchange of knowledge, best practices, and emerging trends related to nitrosamine impurities. This collaborative effort will contribute to a more comprehensive and unified approach to risk assessment and control.

Additionally, continuous monitoring and updates are crucial. As new information and scientific evidence emerge, it becomes imperative to adapt and refine risk assessment strategies.

I bring this more ‘philosophical’ perspective to see if we get closer to proactive behavior (being the driver of the vehicle) rather than reactive.


I could not agree more

1 Like