Evaluation of Hydroxyethyl Cellulose Grades as the Main Matrix Former to Produce 3D-Printed Controlled-Release Dosage Forms.

Diclofenac sodium tablets were successfully prepared via hot-melt extrusion (HME) and fused deposition modeling (FDM), using different molecular-weight (Mw) grades of hydroxyethyl cellulose (HEC) as the main excipient. Hydroxypropyl cellulose (HPC) was added to facilitate HME and to produce drug-loaded, uniform filaments. The effect of the HEC grades (90-1000 kDa) on the processability of HME and FDM was assessed. Mechanical properties of the filaments were evaluated using the three-point bend (3PB) test. Breaking stress and distance were set in relation to the filament feedability to identify printer-specific thresholds that enable proper feeding. The study demonstrated that despite the HEC grade used, all formulations were at least printable. However, only the HEC L formulation was feedable, showing the highest breaking stress (29.40 ± 1.52 MPa) and distance (1.54 ± 0.08 mm). Tablet drug release showed that the release was Mw dependent up to a certain HEC Mw limit (720 kDa). Overall, the release was driven by anomalous transport due to drug diffusion and polymer erosion. The results indicate that despite being underused in FDM, HEC is a suitable main excipient for 3D-printed dosage forms. More research on underutilized polymers in FDM should be encouraged to increase the limited availability.