Nitrosamine (NDSRI) impurity standards

Why nitrosamine impurities are still the hardest part of an impurity strategy

Nitrosamines are a structurally defined class of N-nitroso compounds, many of which are classified as probable human carcinogens. Because the class alert is structural rather than tied to one manufacturing route, a nitrosamine risk assessment now covers the active substance, every starting material and intermediate, the excipients, the packaging, and the drug product itself.

The harder half of the problem is analytical. A nitrosamine impurity is usually present at trace level inside a much larger peak of the parent amine, and the confirmatory method has to resolve a compound that is often only a few mass units away from the substance it came from. That is why a characterised reference standard — not a working solution made in-house — is normally the limiting reagent when a method is being validated.

NDSRIs (nitrosamine drug substance-related impurities) are the subset formed from the drug molecule itself, usually at a secondary or tertiary amine. They carry the same structural alert but are specific to one API, so no generic reference standard exists for them: each one has to be synthesised and characterised on its own. This is where most of our work sits, and it is why the catalogue below is organised by parent drug.

If you are at the specification stage rather than the ordering stage, the nitrosamine reference standard buying guide covers the part that decides everything downstream: converting an acceptable intake in ng/day into a ppm limit for your maximum daily dose, why the FDA and EMA category 1 values differ, and what the certificate of analysis then has to state.

All products on this page are reference materials for pharmaceutical research and analytical development. They are not for diagnostic, therapeutic or human use.