Effect of Drug-Excipient Interactions on the Properties of Mefenamic Acid Particles: A Laboratory Experiment for Pharmacy Undergraduates

Abstract

In pharmaceutical formulations, excipients are not inert additives but critical determinants of the solid-state properties, dissolution performance, and oral bioavailability of active pharmaceutical ingredients (APIs). Therefore, an understanding of the intrinsic mechanisms behind the interactions between drugs and excipients has become a core fundamental competency for pharmacy undergraduates. Traditional pharmacy curricula are still predominantly focused on theory with limited practical sessions, which leaves students unable to effectively translate their theoretical knowledge into practical application. To address this pedagogical gap, we designed a four-week comprehensive experiment course, including the preparation and characterization of particles using mefenamic acid (MA) as an API and three excipients (Poloxamer 188, HPMCAS, and Eudragit L100) for pH-driven coprecipitation. The particles were systematically characterized using laser particle size analysis, scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), and proton nuclear magnetic resonance spectroscopy (¹H NMR). The data analysis elucidated that intermolecular interactions are the core regulatory mechanism. The assessment results for participating undergraduate students show that the intended learning objectives were fully achieved. The main outcomes included bottom-up particle preparation, solid-state characterization, and mechanistic analysis of hydrogen bond interactions between drugs and excipients. This experiment seamlessly integrates theory and practice by rational excipient selection and provides a robust, resource-adaptable teaching module to equip students for pharmaceutical R&D careers.