The effects of recycling pharmaceutical formulations in laser powder bed fusion 3D printing - the influence of physical phenomena on printing performance.

Laser powder bed fusion is an attractive technology for 3D printing objects in a powder bed and has been explored for printing pharmaceutical dosage forms, such as tablets. Recycling of non-sintered residual powder is not well understood, but is critical to prevent economic losses and improve the sustainability of this technique. We investigated the recyclability of three pharmaceutical formulations in the context of laser powder bed fusion of tablets. Three formulations consisting of common pharmaceutical polymers and the model drug indomethacin have been investigated up to ten print cycles. For each print cycle, powder and tablet samples were collected and analyzed for ageing phenomena. Results showed that polyvinyl alcohol and methacrylic acid-ethyl acrylate copolymer-based formulations were recyclable without changes in critical quality attributes of printed dosage forms for 5 and 9 cycles, respectively. A copovidone-based formulation showed a gradual increase in particle size over 10 cycles, resulting in a gradual decrease in tablet weight. This formulation was considered non-recyclable under the conditions evaluated in this work. The observed ageing phenomena were mainly related to changes in particle size, powder cohesion, and glass transition temperature. It is shown that considering powder ageing during formulation development is critical for optimal print performance and further development of laser powder bed fusion for pharmaceutical applications.