Plasticizer-Driven Modulation of Processability and Performance in HME-Based Filaments and FDM 3D-Printed Tablets

This study investigated the effects of different types and ratios of plasticizers on the fabrication and properties of hot-melt-extruded filaments and fused deposition modeling (FDM) three-dimensional printed tablets containing theophylline (THEO). Polyethylene glycol (PEG) 1500 and stearic acid (SA) were used as plasticizers to prepare THEO-loaded filaments in a hydroxypropyl cellulose matrix via hot melt extrusion (HME), which were subsequently fabricated into tablets using an FDM 3D printer. The physicochemical properties of the filaments and printed tablets were evaluated using scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. Drug release behavior was assessed using four tablet formulations (T1–T4) with different plasticizer types and ratios. All fabricated filaments exhibited sufficient hardness and flexibility for reliable 3D printing, and solid-state analyses confirmed partial molecular dispersion of THEO within the polymer matrix. In dissolution studies, PEG-containing formulations showed faster drug release than SA-based formulations, while all 3D-printed tablets achieved approximately 80% drug release within 6 h. Overall, this study demonstrates that the combined use of HME and FDM-based 3D printing, together with rational plasticizer selection, enables the development of personalized pharmaceutical tablets with tunable immediate and sustained drug release profiles.