A process for preparing and isolating pharmaceutical active ingredient particles having a particle size of between about 0.1 and 30 microns, wherein a slurry comprising the active ingredient and one or more pharmaceutically acceptable excipients is fed into a thin film evaporator under suitable conditions for less than 10 minutes sufficient to generate solid matrix particles comprising active ingredient and one or more excipients, wherein the particles have less than 5% residual solvent.