Milling ANd Size Reduction

Milling is used across a number of different industries and can be broadly divided into two types: wet milling and dry milling. 

When it comes to the manufacturing of pharmaceuticals, the particle size of ingredients is critical to a drug’s performance and efficiency, so the stakes are much higher than when milling foods or other consumer goods. Choosing between wet milling and dry milling for a specific active pharmaceutical ingredient (API) requires careful consideration and a keen understanding of both methods of particle size reduction.

Milling is quite simple, applying energy through mechanical forces to break down particles into smaller sizes. This can be accomplished by using grinding media, screens, pegs, pebbles, or rods; the process may also be described as grinding, granulation, size reduction, comminution, or pulverization. 

Milling is a top-down approach that breaks larger particles down into smaller ones, compared with a method like precipitation, which is a bottom-up method that constructs molecules from a dissolved state.

As particles are forced through the mill, they are torn or crushed, thus reducing their size. Milling is used for a number of different purposes in different industries, but in the pharmaceutical industry, this type of mechanical size reduction is used to control the size of APIs, reagents, and excipients to optimize a drug’s delivery and performance.