Solution degradant of mirabegron extended release tablets resulting from a Strecker-like reaction between mirabegron, minute amounts of hydrogen cyanide in acetonitrile, and formaldehyde in PEG during sample preparation

Publication date: Available online 1 February 2019Source: Journal of Pharmaceutical and Biomedical AnalysisAuthor(s): Jinsheng Lin, Tianpei Huang, Mengxue Feng, Dan Li, Danna Zhao, Jichao Wang, Ji Jianyang, Wenquan Zhu, Min LiAbstractDuring the related substances testing of mirabegron extended release tablets, an unknown peak was observed in HPLC chromatograms in a level exceeding the identification threshold. By using a strategy that combines LC–PDA/UV-MSn with mechanism-based stress studies, the unknown peak was rapidly identified as cyanomethyl mirabegron, a solution degradant that is caused by a Strecker-like reaction between the API, formaldehyde (an impurity in PEG), and HCN (an impurity in HPLC grade acetonitrile). The mechanism of the solution degradation chemistry was verified by stressing mirabegron with formaldehyde and trimethylsilyl cyanide (TMSCN, a synthetic reagent that generates HCN upon contact with water), in which the secondary amine group of mirabegron first reacts with formaldehyde to form the iminium ion intermediate; the latter then undergoes a nucleophilic attack by cyanide to yield the cyanomethyl mirabegron. The structure of the impurity was further confirmed through the synthesis of the impurity and subsequent structure characterization by 1D and 2D NMR. Due to the ubiquitous presence of formaldehyde in pharmaceutical excipients (e.g., PEG and polysorbate) and trace amount of HCN in HPLC grade acetonitrile, this type of solution degradation would...
Source: Journal of Pharmaceutical and Biomedical Analysis - Category: Drugs & Pharmacology Source Type: research