Identification, Synthesis, and Characterization of N-Formyl Mirabegron: A New Degradation Product Formed by Formic Acid Impurity in Pharmaceutical Excipients.

This study demonstrated the impact of formic acid (FAc), a common reactive impurity in pharmaceutical excipients, on the stability of mirabegron (MB). The investigation of MB-excipient compatibility tests revealed the formation of a new degradation product, FAc-DP, at 0.2% after 7 days of isothermal stress at 55°C. FAc-DP was synthesized and characterized as N-formyl MB using liquid chromatography-mass spectrometry (LC-MS) and both 1D and 2D nuclear magnetic resonance spectroscopy (NMR).