Scale-Up of pharmaceutical Hot-Melt-Extrusion: Process optimization and transfer.

Hot-Melt-Extrusion on Twin-Screw-Extruders has been established as a standard processing technique for pharmaceutical products. A major challenge is the transfer from a lab to a production level, since the combination of several unit operations within one apparatus leads to complex conditions for such a continuous manufacturing process. Here the residence time distribution is a crucial measure, which reflects the different mechanisms, e.g. dissolution, mixing or degradation, during processing. In the first part of a Scale-Up study, a methodology for the optimization of an extrusion process with respect to the load and throughput is presented. The developed concept was applied for different extruder scales in order to compare the identified processing windows. A deviation of the dominant material heating mechanisms was observed for the different scales, while the constraints for the transfer of a process to a different scale by the developed optimization concept is demonstrated. Finally, a sufficient operating point on a reference extruder is identified and in the second part of this study, different concepts from literature are applied for the transfer of this Hot-Melt-Extrusion process to two larger scales. The focus of the investigations was on the impact of the different approaches on the residence time distribution and the comparison. The determined results revealed a change of the most sufficient approach for the two different extruder sizes. The impact on the location in the time domain and form of the distribution are discussed and additionally evaluated by the fit to a RTD-model. In conclusion, the ratio of the applied energy for transport to mixing is identified as valuable addition in this context.