O-PTIR spectroscopy for characterizing active pharmaceutical ingredient specific particle size distributions of nasal spray suspension products.

Evaluation of the particle size distribution (PSD) of active pharmaceutical ingredients (APIs) in nasal suspension products is challenging due to the presence of both API and excipients. To characterize these intricate formulations, it is essential to have sophisticated analytical methods that offer high spatial resolution and the ability to chemically pinpoint and map out the presence of API particles. However, such advanced techniques have not been documented for nasal formulations yet. In this proof-of-concept study, we investigated the utility of optical photothermal infrared spectroscopy (O-PTIR) to analyze the PSD of commercially available Nasonex® and its generic Azonaire® nasal mometasone furoate (MM) suspensions. Simultaneous O-PTIR and Raman spectra, as well as IR chemical maps, were collected from the particles in both formulations. Spatially resolved spectra from the particles confirmed the presence of peaks related to MM (1727 cm, 1661 cm, and 1122 cm) and excipient microcrystalline cellulose (MCC) (1061 cm). The PSD of MM particles was characterized using chemical maps specific to MM (1661 cm) and automated imaging. Results confirmed that the PSD of both formulations were comparable. Spectral analysis also revealed the presence of free MM, free MCC, and particles containing co-localized MM and MCC. For suspension-based nasal products, O-PTIR enables the measurement of API PSD, which is critical for formulators in developing nasal suspension products. This approach holds potential as an innovative complimentary analytical tool that could diminish the need for extensive clinical endpoint bioequivalence studies when evaluating the comparability of generic and brand-name nasal suspension products.