A method of co-formulating two or more pharmaceutically active compounds into a particulate product including contacting a dense, supercritical or near-critical fluid With a suspension of a first active compound in a medium that is miscible with the dense fluid and a solution of a second active compound in a solvent that is miscible with the dense fluid. The product may be the first active agent coated with the second active agent. The method may use coaxial nozzles for the fluid, media or solvents. The method may be applied to production of dry powders for inhalation including beta-agonists and corticosteroids. Apparatus for use in the method comprising means for streams of solvents, media and dense fluids to enter a precipitation chamber at substantially the same point and means for collection of particles under gravity in one or more collection chambers.