Secondary Drying: Challenges and Considerations

Secondary drying refers to the final stage of lyophilization where one removes bound water from the remaining product. Optimizing secondary drying is essential for pharmaceutical products because 10–20% of the total drying time and 12–20% of the operational cost comes from this process. This chapter will provide a literature review of secondary drying and describe the current state-of-the-art in this field. Topics covered include an overview of heat and mass transfer modeling, experimental characterization techniques, critical process variables affecting the secondary drying, and technical challenges in the field. Such information will hopefully provide basic insight into the secondary drying process and act as a starting point for those seeking advice to understand and optimize this process.