Development of Spray-Dried Mannitol–Pregelatinized Rice Starch Using SeDeM-Based Approach for Direct Compressible Cetirizine Dihydrochloride Tablets

Background/Objectives: Direct compression offers a cost-effective route for tablet manufacturing but is often limited by poor powder flow and compressibility. This study reported the development of a co-processed excipient comprising 98% mannitol and 2% pregelatinized rice starch (PRS) using spray drying with ammonium bicarbonate as a pore-forming agent. Methods: This optimized excipient demonstrated balanced powder flow and enhanced compressibility suitable for direct compression applications. The SeDeM expert system guided the optimization process by evaluating raw and spray-dried components. PRS exhibited excellent flowability that decreased after spray drying but displayed significantly enhanced compressibility, whereas mannitol maintained superior flow but continued to show limited compressibility post-drying. Scanning electron microscopy, differential scanning calorimetry, Fourier-transform infrared spectroscopy, and X-ray powder diffraction confirmed the absence of chemical interactions and unchanged wettability during co-processing. Results: The resulting excipient combined the favorable flow characteristics of mannitol with the improved compressibility of PRS, rendering it suitable for direct compression. Cetirizine dihydrochloride (CET) tablets were formulated via exponential curve fitting within the SeDeM framework, yielding an optimal CET-to-excipient ratio of 13:87. The tablets met all pharmacopeial physicochemical requirements, including uniform mass, adequate tensile strength, rapid disintegration, and dissolution profiles comparable to a reference product, with dissimilarity (f1 = 4.28) and similarity (f2 = 64.03) factors within regulatory acceptance limits. Conclusions: These findings represented the first application of SeDeM methodology to a co-processed mannitol–pregelatinized rice starch system, enabling predictive optimization of powder flow and compressibility in direct compression formulations.