Analytical method development for characterizing ingredient-specific particle size distributions of nasal spray suspension products.

Particle size characterization for active pharmaceutical ingredients (APIs) in nasal spray suspension products presents unique challenges because both the API and excipient particles are present in the final dosage form. Currently, an established method is lacking because traditional particle sizing technologies do not distinguish the chemical identity of the particles. In this study, a non-destructive, ingredient-specific particle sizing method was developed for characterization of mometasone furoate (MF) nasal spray suspensions using Morphology Directed Raman Spectroscopy (MDRS). A five-step method development procedure was used in this study: sample preparation, particle imaging and morphology analysis, particle Raman measurements and classification, morphology filter selection, and minimum number of particles determination. Wet dispersion sample preparation method was selected to ensure that the particles were measured in their original suspended state. A training set containing over 10,000 randomly-selected particles, including both the API and excipient particles, was used to gain a comprehensive understanding of particle size, shape, and chemical ID for the nasal spray suspension. Morphology and Raman measurements were performed on each particle in the training set. The measurement results suggested that the aspect ratio and intensity mean filter combination was an appropriate morphology filter setting to selectively target API particles and exclude most of excipient particles. With further optimization of the morphology filter cutoff values and determination of minimal number of particles to be measured, the total measurement time was reduced from 90 hours to 8 hours. The morphologically screening strategy ultimately allowed us to create a time-efficient practical API-specific particle size distribution (PSD) methods for nasal spray suspensions. This study shows that MDRS is a fit for purpose analytical technique for determining ingredient-specific PSDs of the pharmaceutical formulation studied in this work.