Investigation of semi-solid formulations for 3D printing of drugs after prolonged storage to mimic real-life applications

The implementation of tailor-made dosage forms is currently one of the biggest challenges in the health sector. Over the last years, different approaches have been introduced to provide an individual and precise dispensing of the appropriate dose of an active pharmaceutical ingredient (API). A more recent approach, which has been intensively researched in the last years, is 3D-printing of medicines. The aim of this work was to develop printing formulations free of organic solvents for a pressure-assisted microsyringe printing method (PAM), which should also be printable over several days of storage. Furthermore, the printed dosage forms should provide a sustained release of the incorporated API. A mixture of polyvinyl acetate/polyvinylpyrrolidone copolymer (PVAc-PVP), hydroxypropyl methylcellulose (HPMC) and highly dispersed silicon dioxide (SiO₂) was found to be a feasible polymer matrix to achieve a sustained drug release. Levetiracetam (LEV) was used as model drug. The printed formulations were analyzed regarding mass variation, friability and thickness. Furthermore, the dissolution behavior of freshly printed tablets and tablets printed from stored printing formulations were investigated. The dissolution profiles indicate that the dissolution of LEV could be modified by varying the amount of HPMC and by changing the infill design of tablets. Tablet-like geometries with an infill design of 0.35 mm and 5% HPMC released 50% of the incorporated drug after 4 h, while for tablets with a higher HPMC amount the release was decreased (10% HPMC: 5.5 h; 15% HPMC: 8 h). All printed tablets exhibit a friability < 0.5%, indicating that PAM printing is suitable for the manufacturing of tablets with a high structural integrity. Furthermore, this study demonstrates the ability of producing tablets with a uniform content and mass using PAM printing.