A novel approach to sterile pharmaceutical freeze-drying

Evaluation of Packaging Materials in Freeze-Drying: Use of Polymer Caps and Nested Vials and Their Impact on Process and Product Attributes

Current trends in the pharmaceutical industry led to a demand for more flexible manufacturing processes with smaller batch sizes. Prepackaged nested vials that can be processed as a unit were introduced into the market to fulfill this need. However, vial nests provide a different thermal environment for the vials compared to a hexagonal packaging array and could therefore influence product temperature profiles, primary drying times, and product quality attributes. Polymer caps with the possibility of vial closure inside the freeze-drying chamber were developed to remove the risks and need of a crimping process. A general concern with the use of such caps is the possibility of an increase in resistance to water vapor flow out of the vial. This case study investigated the effect of the LyoSeal^® and PLASCAP^® polymer caps and EZ-fill^® nests on the freeze-drying process. Amorphous and partially crystalline model formulations were freeze-dried. Process data and product quality attributes were compared for regularly stoppered vials and vials with polymer caps as well as vials in a hexagonal packaging array and nested vials. The results indicated no increased resistance or impeded water vapor flow by the polymer caps. Differences in the macro- and microscopic appearances of products and a trend towards lower product temperatures were observed for the investigated nest type compared to a regular hexagonal packaging array. Consequently, the polymer caps could be used as an alternative to regular stoppers without affecting freeze-drying process data or product quality attributes, while the different thermal environment of nested vials should be considered.

Freeze-drying in protective bags: Characterization of heat and mass transfer

During lyophilisation of highly potent Active Pharmaceutical Ingredients (APIs) potential contamination of the freeze-drier is an important safety issue. Since the stoppers are in semistoppered position during the lyophilization process, API may contaminate the chamber and cross-contamination may occur as well. In this study two protective bags, which enclose each tray and their influence on heat and mass transfer during freeze-drying were investigated. Sublimation tests were performed using either purified water or solutions containing trehalose as well as hydroxypropyl-β-cyclodextrin (HPbCD) as bulking agents. During sublimation tests with purified water both bags clearly influenced heat and mass transfer compared to unpacked reference vials. The bag, which was originally designed to be used for steam sterilization, had a massive impact on drying characteristics. The bag membrane becomes the rate limiting factor, generating a separate compartment within the bag. In this compartment vapor pressure is much higher compared to the chamber pressure during primary drying, leading to altered drying conditions. However, drying was still possible. The other bag, which was specifically designed for lyophilization, also had an impact on drying behavior which could be assigned to the foil between shelf and bottom of the vials. This was detectable as differences in K_v values. Membrane resistance, however, becomes negligible when 10% (w/w) trehalose or HPbCD solutions were dried using the later bag as containment. The data reported in this work demonstrate the relevance and value of sublimation tests to understand the lyophilization process, especially when new components are implemented. The data should be considered, when freeze-drying shall be performed using such bags.