Pharmaceutical Evaluation of Levofloxacin Orally Disintegrating Tablet Formulation Using Low Frequency Raman Spectroscopy

We evaluated the pharmaceutical properties of levofloxacin (LV) in the form of an orally disintegrating tablet (LV(ODT)) to find a new usefulness of low frequency (LF) Raman spectroscopy. LV(ODT) contained dispersed granules with diameters in the order of several hundred micrometers, which were composed of the active pharmaceutical ingredient (API), as confirmed by infrared (IR) microspectroscopy. On the contrary, the API and inactive pharmaceutical ingredients (non-APIs) were homogeneously distributed in LV tablet (LV(T)) formulations. Microscopic IR spectroscopy and thermal analyses showed that LV(ODT) and LV(T) contained the API in different crystalline forms or environment around the API each other. Furthermore, powder X-ray diffraction showed that LV(T) contained a hemihydrate of the API, while LV(ODT) showed a partial transition to the monohydrate form. This result was confirmed by microscopic LF Raman spectroscopy. Moreover, this method confirmed the presence of thin layers coating the outer edges of the granules that contained the API. Spectra obtained from these thin layers indicated the presence of titanium dioxide, suggesting that the layers coexisted with a polymer that masks the bitterness of API. The microscopic LF Raman spectroscopy results in this study indicated new applications of this method in pharmaceutical science.