Predicting particle size of a model drug micronized by jet milling


*Corresponding author
Hovione FarmaCiencia SA, R&D Drug Product Development, Sete Casas, 2674 – 506 Loures, Portugal


Jet mills are widely used in the pharmaceutical industry when particle size reduction is required to increase drug bioavailability or to provide powders with fine-tuned aerodynamic properties. The main disadvantage of jet milling is the large amount of energy required for the micronization process. A good process understanding is fundamental to master the technique and avoid costly reworks. In this work, a semi-empirical approach was applied to predict the particle size of a model drug micronized by jet milling based on the operating conditions and on the particle size of the starting material. The results obtained show that particle size relates well with the specific energy imparted to the system. A critical value of the specific energy was defined above which the increase in the energy input has less impact on particle size reduction.


Jet milling is a grinding process in which a gas in vortex motion is used to impact particles against each other in a grinding chamber, resulting in powders with a smaller particle size. Jet mills are ideal when narrow particle size distributions are required and for handling materials of high purity or heat sensitive materials due to the cooling effect of the gas jets. In addition, jet milling is a simple unit operation that requires low maintenance and operational costs. The main disadvantage of jet milling, when compared to other milling technologies, is related with the high amount of energy required for the grinding operation (1, 2).

The regulatory agencies have the common aspiration to see pharmaceutical companies have a systematic approach during development phases, ideally a Quality by Design (QbD) approach, which begins with predefined objectives and emphasizes process and product understanding and process control, based on sound science and quality risk management (3). The benefits of using such approach include a better understanding of the process, less batch failure, more efficient and effective control of change and cost savings ...