Formulation development and process analysis of drug-loaded filaments manufactured via hot-melt extrusion for 3D-printing of medicines

Three dimensional(3D)-printing via fused deposition modeling (FDM) allows the production of individualized solid dosage forms. However, for bringing this benefit to the patient, active pharmaceutical ingredient (API)-loaded filaments of pharmaceutical grade excipients are necessary as feedstock and have to be produced industrially. As large-scale production of API-loaded filaments has not been described in literature, this study presents a development of 3D-printable filaments, which can continuously be produced via hot-melt extrusion. Further, a combination of testing methods for mechanical resilience of filaments was applied to improve the prediction of their printability. Eudragit RL was chosen as a sustained release polymer and theophylline (30%) as thermally stable model drug. Stearic acid (7%) and polyethylene glycol 4000 (10%), were evaluated as suitable plasticizers for producing 3D-printable filaments. The two formulations were printed into solid dosage forms and analyzed regarding their dissolution profiles. This revealed that stearic acid maintained sustained release properties of the matrix whereas polyethylene glycol 4000 did not. Analysis of the continuous extrusion process was done using a design of experiments. It showed that powder feed rate and speed of the stretching device used after extrusion predominantly determine the diameter of the filament and thereby the mechanical resilience of a filament.