Analyzing Nitrosamines

In ranitidine what are the drawbacks for detecting NDMA by GC method?
It has been demonstrated that high temperatures, such as those used in GC injection ports and column ovens, will result in overestimation of NDMA in ranitidine samples due to the thermal degradation of ranitidine and subsequent formation of NDMA. Therefore it is highly recommended that LC-MS be used for determination of NDMA in Ranitidine drug substance and drug products.

Can you please share any nitrosamines methods using detectors other than MS/MS?
Unfortunately, UV (and RI) detection is not nearly sensitive enough to achieve the low levels of detection (as low as 0.03 ppm being required in early 2021) that will be required for nitrosamines. This is partly due to the lack of a strong chromophore in nitrosamines. MS detection is sensitive and specific enough to allow for identification and quantitation, as well as continued monitoring for the required levels of nitrosamine impurities in drug substances and products.

Which columns / stationary phases have proven the most useful for separating and detecting nitrosamine impurities in drug substances and drug products?
Several different stationary phases have been tested and proven capable for the analysis of genotoxic nitrosamine impurities; these include both core-shell silica columns (Kinetex F5 and Biphenyl) and fully porous silica columns (Luna Omega PS C18).

Which method do we have to follow; published FDA (or other regulatory agency such as EMA) methods, or our in-house validated methods?
Generally, FDA published testing methods are intended to provide options for industry; specifically, here for the determination of nitrosamine impurities in various drug substances and drug products. These methods should be validated by the user if the resulting data are used to support a required quality assessment of the drug substance and/or drug product, or if the results are used in a regulatory submission.

You can use an in-house validated method, provided your method is capable of achieving the low levels (LOD and LOQ) of detection for genotoxic nitrosamine impurities required by regulators.

Genotoxic nitrosamine impurities have been observed in various ‘sartan’ drugs manufactured by many different companies using different routes of manufacturing; has a specific probable cause been identified for the formation of these impurities?
There has been a lot of speculation regarding probable causes for the formation of these genotoxic impurities in sartan drugs. Since work continues to identify and confirm potential causes for the formation of these impurities, we recommend you view the latest information on the FDA and EMA websites.

If DMF is not involved in the manufacturing of Ranitidine, how is it possible for NDMA to have been found in this drug product?
The Ranitidine molecule contains both nitrite and dimethylamine groups, which have been shown to react to produce NDMA. It is believed that this pathway is the source for NDMA found in Ranitidine drug product. It has further been demonstrated that this degradation reaction is accelerated by heat, as evidenced by the very high levels of NDMA detected in Ranitidine tested under GC-MS conditions (130 °C oven) which Valisure reported in their Citizen’s Petition to the FDA. This potential pathway for formation of NDMA during storage is one reason that this drug has been pulled from the market.

Which nitrosamines can be analyzed with the currently available analytical methods from FDA?

• a. N-nitroso-dimethylamine (NDMA)
• b. N-nitroso-diethylamine (NDEA)
• c. N-ethyl-N-nitroso-2-propanamine (NEIPA)
• d. N-nitroso-diisopropylamine (NDIPA)
• e. N-nitroso-di-n-propylamine (NDPA)
• f. N-nitroso-methylphenylamine (NMPA)
• g. N-nitroso-di-n-butylamine (NDBA)
• h. N-nitroso-N-methyl-4-aminobutyric acid (NMBA)

Can you please share sample preparation methods using SPE?
Unfortunately, at this time an SPE method has not been successfully developed. The primary challenge relates to the volatility of the nitrosamines, especially NDMA and NDEA, which result in very poor recoveries during the elution and dry down steps.

To date the most common sample preparation scheme is to dissolve a known weight of drug substance or drug product into a known volume of methanol, and shake vigorously (manually, with mechanical shaker, or centrifuge), then filter supernatant prior to injection.

Specific details can be found in the FDA methods for ARB drugs (sartans), ranitidine, and metformin.