The following description refers to a process for the impregnation of cross-linked polymers with an active ingredient. The process is based on the used of compressed fluids, in particular CO2, with antisolvent effect, and involves the steps of impregnating the polymer with an active ingredient solution, adding a compressed fluid until precipitation of the active ingredient caused by the compressed fluid antisolvent effect, removing the solvent and the compressed fluid. The process allows to obtain accelerated release pharmaceutical formulations that, compared with the formulations already known, contain larger quantities of amorphous or nanocrystalline active ingredient.