An investigation into the effects of geometric scaling and pore structure on drug dose and release of 3D printed solid dosage forms

A range of 3D printing methods have been investigated intensively in the literature for manufacturing personalised solid dosage forms, with infill density commonly used to control release rates. However, there is limited mechanistic understanding of the impacts of infill adjustments on in vitro performance when printing tablets of constant dose. In this study, the effects and interplay of infill pattern and tablet geometry scaling on dose and drug release performance were investigated. Paracetamol (PAC) was used as a model drug. An immediate release erodible system (Eudragit E PO) and an erodible swellable system (Soluplus) were prepared via wet granulation into granules and printed using Arburg Plastic Freeforming (APF). Both binary formulations, despite not FDM printable, were successfully APF printed and exhibited good reproducibility compared to pharmacopoeia specification. The physical form of the drug and its integrity following granulation and printing was assessed using DSC, PXRD and ATR-FTIR. Two infill patterns (SM1 and SM2) were employed to print tablets with equal porosity, but different pore size, structure and surface area to volume ratio (SA/V). Geometry scaling (tablet height and diameter) of Eudragit-PAC tablets was not found to significantly influence the release rate of the tablets with 30 to 70% infill density. When increased to 90% infill density, geometric scaling was found to have a significant effect on release rate with the constant diameter tablet releasing faster than the constant height tablet. Soluplus-PAC tablets printed using different infill patterns demonstrated similar release profiles, due to swelling. Geometric parameters were found to significantly influence release profiles for tablets printed at certain infill densities giving new insight into how software parameters can be used to tune drug release