3D Printing of Hydrocortisone-loaded Eudragit RS Tablets: Influence of Plasticizers and Their Concentration on the Printability of Filaments

Although FDM is one of the prominent 3D printing technologies, and it has been widely investigated in pharmaceutical sciences, the printability of filaments remains a challenge. Therefore, our primary objective was to evaluate the effect of PEG 400, PEG 4000 and triethyl citrate at different concentrations (10%, 15% and 20% w/w) on the printability behavior of hydrocortisone-loaded Eudragit RS filaments. In this study, physical mixtures and their filaments were produced using a hot melt extruder and the properties of the filaments were examined by DSC, XRD, FESEM, FTIR, MFI and mechanical tests. Release behavior and hardness properties of the 3D-printed tablets were also evaluated. DSC and XRD results showed that the drug converted from crystalline to amorphous during hot melt extrusion and remained so during the 3D printing. FTIR results showed no chemical interactions between the drug and other excipients during hot melt extrusion and 3D printing. FESEM results of filaments showed that triethyl citrate-containing filaments had rougher surfaces, which makes them more suitable for 3D printing, while PEG-contained filaments had smoother surfaces. Mechanical tests showed that filaments containing triethyl citrate were stronger and tougher and had moderate ductility and stiffness. Overall, these filaments showed a good balance between these mechanical characteristics, which makes them a suitable candidate for 3D printing. Release studies showed that regardless of plasticizer type, the concentration of the plasticizer determines the extent of drug release. MFI test showed that formulations containing TEC presented a melt flow closer to 30 g/10 min compared to other formulations. Therefore, it can be deduced that TEC improves printability by enhancing melt flow better than the other two plasticizers (PEG 400 and PEG 4000). Based on the results, it can be concluded that triethyl citrate in 15% concentration is the best plasticizer for the production of hydrocortisone-loaded Eudragit RS tablets.