NDMA in macrolides: GC-MS/MS method for its detection and study of its formation.

N-nitrosodimethylamine (NDMA) is the most commonly found N-nitrosamine in pharmaceutical drug substances (DSs) and drug products. This paper investigates the potential of macrolide antibiotics, containing dimethylamino group, as precursors for NDMA formation in pharmaceuticals. A direct injection GC-MS/MS method was qualified for the quantification of NDMA in various macrolide DSs and film-coated tablets, and the use of pyrrolidine as a scavenger was further emphasized. As an alternative method, GC-MS/MS method with solid phase microextraction was tested, which proved to be unsuitable due to the limited water solubility of macrolides. However, its applicability was confirmed for the analysis of NDMA in water-soluble DSs, such as metformin. The observations regarding the solubility can be applied to a wide range of drug products and analytical methods for the accurate determination of nitrosamines. Various macrolide DSs showed significant levels of NDMA, confirming macrolides as NDMA precursors. In macrolide film-coated tablets, NDMA traces of up to about 70 ppb and 165 ppb were found in azithromycin and spiramycin, respectively, greatly exceeding the acceptable intake limit for NDMA. These findings confirmed the potential of macrolides for NDMA formation which was further enhanced in spiramycin that contains two dimethylamino groups. Furthermore, it has been shown that a stable DS form can successfully prevent NDMA formation, as observed with azithromycin dihydrate. The NDMA content in macrolides can also increase significantly during storage as shown in an accelerated stability study, which together with the levels above the AI limits highlights the need for greater attention and consideration.