MILLING OPERATIONS IN THE PHARMACEUTICAL INDUSTRY

Milling is a powerful unit operation to aid in the control of particle size for a variety of processing, bioavailability, reactivity, and safety-related drivers. This chapter provides some guidance on how to use the information to select milling equipment and the key parameters that can influence its performance. The resulting mean particle size and particle size distribution depend not only on the mill but also on physical properties of the feed solids such as brittleness and hardness, as well as its initial size distribution. Generally speaking, the most efficient way to assess milling feasibility is to perform trial experiments that can be combined with mechanistic tools to describe particle breakage. However, engineering understanding of mill operation and key process parameters permits effective scale-up of milling, so that the particle size to be achieved at large scale can be predicted accurately from carefully conducted gram-scale bench experiments.