A method for enlarging the particle size of crystalline microparticles of active substance by providinga first suspension prepared from crystalline microparticles of active substance with a first d50 value of 0.5-5 μm, solvent and antisolvent for the active substance, wherein the solubility of the active substance in the solvent-antisolvent mixture of the first suspension is 0.001-0.5 wt. %, such that the average particle diameter (d50 value) at the end or the method is at least 0.03 μm larger than the starting d50 value. The d50 values of a first batch can also serve to control the particle coarsening of a second batch. In addition, particles of fluticasone propionate having an average particle size d50 of 1.0-1.5 μm and simultaneously a narrow particle size distribution with a span <；1.35 and high crystallinity with an amorphous fraction of <；0.5 wt. % can be prepared.
