Luminescence Spectroscopy as a Tool to Study the Amorphization of Indomethacin upon Co-Grinding with Polymers

The possibility of using luminescence spectroscopy to study even the early stages of the amorphization of active pharmaceutical ingredients (APIs) during their co-grinding with different polymers has been demonstrated using indomethacin as an example. Amorphization of an API is observed only on co-grinding with those polymers that have functional groups capable of interacting with the API to form supramolecular complexes. It is the formation of supramolecular complexes due to the chemical affinity between them, rather than local heating caused by plastic deformation of an API or of a polymer, that is responsible for the amorphization of the API on co-grinding with selected polymers. It has also been shown that luminescence spectroscopy can be a sensitive method of monitoring the crystallization of the amorphous phase of APIs during storage of API mechanocomposites with polymers depending on temperature and relative humidity.