I’m currently working on a comprehensive webinar on our favorite subject. For anyone interested, here’s a link: The Regulatory Requirements on Nitrosamines in the Pharmaceutical Industry Training Course. In writing this, I’ve been frequently reminded of my journey and a number of things I wish I had known earlier. What are yours? Or, what is something more people should know?
For myself, I would say the outsized risk that desmethyl impurities add to nitrosamine formation in dimethyl tertiary amine APIs. They can be difficult for API manufacturers to remove and from our n=1 study, are >40x more reactive than the original API.
Hi Jason, can you expain a bit the last paragraph. I did my Ph.D. under Dr. Richard Loeppky, who was really the father of tertiary amine nitrosation, though my work was more on beta oxidized nitrosamines. So, I am really interested in understanding what your study indicated.
What we did was by no way definitive. Simply, we performed an abbreviated NAP test in both a dimethyl tertiary amine and its desmethyl impurity. We saw 40x more nitrosamine formation in the desmethyl sample. The actual number is likely higher as the API did contain that same impurity, raising its rate.
We’re sure there are many factors that control this rate. However, it does speak to the outsized contribution to the total nitrosamine formation. This may be even more pronounced when formation is occurring quickly, like during processing vs shelf life. There is a lot more conjecture than knowledge there, admittedly.
Where to begin! But is that an answer to your question on what I wish I had known at the start of nitrosamines, or a question to myself about how to answer your question?
A few things I wish that I had known at the beginning:
using deuterated standards as internal standards to quantify NDSRIs, instead of direct addition methods - even though they were tricky/expensive to get hold of at the beginning (and you still have to be careful nowadays)
the unexpected consequences on the formation of nitrosamines from different manufacturing processes, and the fact that we now have to almost consider air as an excipient (processing aid?) in the manufacture of products
that NDSRIs would become such a big thing, in terms of levels/discovery compared to the small molecule nitrosamines - focusing time onto NDSRIs at the very beginning would have made discovery easier
So many more things that I could list. It has been one long journey of learning, and it isn’t over yet.
Great thread Jason and very interesting…its a very nice motive to look back in order to move on.
One question on your post because i think i miss something. You said that you find out that the nitrosation of the desmethyl derivatives of the dimethyl tertiary amines far more easier than the nitrosation of them it selves. But this is logical, isn’t? As the desmethyl impurities are secondary amines.
On the question of your thread, i wish i had understand earlier that we should not trust very ‘‘easy’’ the impurities manufacturers. It has been proved several times that for the validity of the reference standards of the NDSRIs the classical NMR spectra (proton and carbon) are not enough and the 2D-NMR (H-H and C-H) are necessary.
thanks
Christos
Chris, I agree. It is logical that desmethyls would react more quickly. Frankly, I just had not even given it a thought until it was staring me in the face as a problem. Also, I was surprised that they were so common.
I completely agree on the quality of standards. This has been a real issue. There are really only 2 providers we trust.
To be honest, i was thinking that the desmethylation is very difficult in the solid state but recently we had an example which we had a result that proved the opposite.
Great reflections @jason.brown … personally, if only I had known… that my professional development would become before and after Nitrosamines. This community today has been a big part of that before and after.
If you allow me, I would like to invite others in the community to share their thoughts/reflections … I’ve been frequently reminded of my journey [on Nitrosamines] and a number of things I wish I had known earlier. What are yours? Or, what is something more people should know?
Initially, I was also surprised to see the level of desmethyl impurities in tertiary alkyl products. However, I still defer from nitrosative dealkylation pathway.
@jason.brown I agree with you that removing desmethyl impurities is challenging, especially in tertiary amine salt APIs.
If regulators had known that nitrosamine mitigation would take such an enormous time and resources, the established timeline would be 10 years rather than 3 years.
Nitrosamines are the revenge of the Organic chemists who have been so many years in the shadow of Analytical chemists and pharmacists in the field of the generic pharmacy
To me the biggest shock was the ubiquitous nature of nitrite and its ability to react in the drug product to produce NDSRI’s. 5 years ago who would have believed this.
I think I have been talking about this issue with N, N-dimethylamines and their nitrosation since Ranitidine issue was talked about. During my stay at NCI, we have seen many of the tertiary amines with N, N-dimethylamino groups have traces of NDMA. Also, my PhD topic was NDELA, which is found to be present in significant amounts in triethanol amine, a common component of cosmetics. But I guess it is an inconvenient truth and people like to pretend that teritiary amines are no danger.
If you read any old papers of nitrosamines, published before this saga started in 2018, you would seen the term “ubiquitous” used repeatedly. Nitrite is also our savior from a lot of infections. And due to nitrogen fixation, abundant in soil, pulled by plants (xylem and phloem) and then consumed by animals. We also make a lot of nitrite in our body due to presence of nitric oxide which is the EDRF, a critical chemical in our bodies. Its interesting that it came as such a surprise.
Maybe worth clarifying the “surprise” element to this.
Of course, nobody is surprised tertiary amines and particularly the dimethyl ones can be a source of nitrosamine risk. It was the question how that risk of formation at DP level would be proportionally divided between (1) dealkylative nitrosation and (2) dealkylation and subsequent nitrosation (manufacturing or shelf life) and (3) nitrosation of secondary amine impurity already present in the input API.
That was a question which was solved in the state of the art maybe already for stoichiometric nitrosation (even on some of the NDSRIs; often signs of dealkylation followed by nitrosation rather than dealkylative nitrosation), but as impurity chemistry for different DP matrices this was often quite new work that was being conducted by Industry, leading to also revisiting the mechanism of demethylation via N-oxide formation and subsequent non-classic Polonovski reaction to the demethylated impurity and the oxygen and moisture controls that are needed to prevent this reaction as much as possible. While typically it is still the case that the nitrosation happens on the secondary amine impurity rather than the tertiary amine API, there are also medicines possible which were already so optimized for the API demethylation that tertiary amine dealkylative nitrosation matters again. Packaging can influence the overall picture here, and the surprise element is also that for the secondary amine nitrosation effect to kick in you might have to wait quite a big part of shelf life (starting in a linear phase before going to an exponential formation phase dominated by secondary amine nitrosation over shelf life). Additionally, the secondary amine is not fairly constant over shelf life like with most APIs, meaning that nitrosation robustness of the analytical method can also differ depending on the time point of testing and require more studies (e.g. matrixed robustness with both nitrites and (labeled) API impurity spikes)). Also, the backbone matters, the more complex substitution part plays a role (not always literature data on the reactivity of the exact tertiary and secondary amine, some are also structurally complex requiring for example assessment of C-nitration and N-nitrosation, with selectivity not per se being the same for secondary and tertiary amine, also not stoichiometrically, whereas lack of selectivity can be a scavenging mode).
There was definitely a surprise element in having to verify with step 2 confirmatory testing whether the overall existing controls on API degradation were also good enough for nitrosamine prevention and I’m sure if you would be able to group all the learnings in this field linked to different APIs it would be still a source of new science due to the complicated mechanistic balance and kinetics.
The occasional positive or negative surprise is not in the pudding but in the eating here.
