This comprehensive study delves into the complexities of achieving bioequivalence for Orally Inhaled and Nasal Drug Products (OINDPs), with a particular focus on the nasal spray suspension formulations. The research primarily revolves around the commercial product Nasonex™ (mometasone furoate monohydrate) and four test nasal suspension formulations containing the same active pharmaceutical ingredient (API). The study meticulously examines the morphology and particle size distribution of both the “as received” API batches and the formulated nasal suspension formulations. The research provides valuable insights into the challenges and potential solutions in achieving bioequivalence for such complex drug products. It underscores the importance of understanding the intricate relationship between the particle size of the API and the release behavior of API when tested under sink conditions. This study is a valuable resource for professionals in the pharmaceutical industry, regulatory authorities, and researchers working on the development and approval of generic orally inhaled and nasal drug products.