A new concept for the continuous freeze-drying of pharmaceutical products in unit doses

The feasibility of the continuous freeze-drying technology has been studied simulating the process using a functional version of the continuous freeze-dryer. Heat transfer during freezing and primary drying was studied reproducing the same conditions occurring in the continuous process. Various process conditions and formulations (containing both amorphous and crystallizing excipients) were investigated in order to better understand the range of applicability of this new process. It has been demonstrated that the cycle duration of the continuous freeze-drying was comparable to that of a conventional batch process, and the aesthetic acceptability of the product was achieved. The continuous freeze-drying technology also impacted positively on inter- and intra-vial heterogeneity. The internal structure of the products, as analyzed by SEM, showed that the continuous freeze-drying led to a structure with larger pores, homogeneously distributed within the product. In addition to these advantages, we have found that the continuous technology can reduce processing time up to 5 times with respect to the batch technology, and the equipment size up to 10 times.