A multi-stage process to control the particle size of a pharmaceutical substance comprising the steps of: passing the pharmaceutical substance through a first stage of a particle size reduction process with a first set of particle size control parameters to obtain a feedstock of reduced median particle size and lesser distribution of median particle size for a second stage of a particle size reduction process passing the feedstock, through a second stage of a particle size reduction process with a second set of particle size control parameters optionally, using the product of the second stage or subsequent stages as a feedstock in further stages of a multi-stage particle size reduction process with a set of particle size control parameters for each stage and collecting a pharmaceutical substance with a median particle size greater than 10 μm and with a narrow, reproducible distribution of median particle sizes.
