A process for the production of nano- and/or microparticles for use in oral administration, which particles contain one or more therapeutic agents dispersed in non-crystalline form in a matrix containing one or more polymers selected from cellulose ethers, cellulose esters, copolymers of methacrylic acid with one or more (meth)acrylic acid esters, copolymers of two or more (meth)acrylic acid esters and mixtures thereof, said process comprising the steps of a) providing a solution containing a1) the one or more therapeutic agents in dissolved form; a2) the one or more polymers in dissolved form, and a3) a solvent mixture containing (i) at least one solvent S1 which is fully miscible with water, and which is a solvent for the one or more therapeutic agents with a solubility of the therapeutic agent(s) in the solvent S1 being 10g/l or higher at 20°C, and a solvent for the one or more polymers, with a solubility of the polymer(s)in the solvent S1 being 100g/l or higher at 20°C, and (ii) at least one solvent S2 which is fully miscible with solvent S1 and which is partially miscible with water, with a solubility of the solvent S2 in water being 1 to 60 wt% of the solvent S2 in relation to the total weight of a mixed phase containing water and the solvent S2 at 20°C; b) adding an aqueous surfactant solution with a volume of at least 2 times the volume of the solution provided in step a) to the solution provided in step a) while the solution provided in step a) is stirred, and c) allowing the nano- and/or microparticles to form via extraction of the solvents S1 and S2 into the aqueous surfactant solution. a) providing a solution containing a1) the one or more therapeutic agents in dissolved form; a2) the one or more polymers in dissolved form, and a3) a solvent mixture containing (i) at least one solvent S1 which is fully miscible with water, and which is a solvent for the one or more therapeutic agents with a solubility of the therapeutic agent(s) in the solvent S1 being 10g/l or higher at 20°C, and a solvent for the one or more polymers, with a solubility of the polymer(s)in the solvent S1 being 100g/l or higher at 20°C, and (ii) at least one solvent S2 which is fully miscible with solvent S1 and which is partially miscible with water, with a solubility of the solvent S2 in water being 1 to 60 wt% of the solvent S2 in relation to the total weight of a mixed phase containing water and the solvent S2 at 20°C; a1) the one or more therapeutic agents in dissolved form; a2) the one or more polymers in dissolved form, and a3) a solvent mixture containing (i) at least one solvent S1 which is fully miscible with water, and which is a solvent for the one or more therapeutic agents with a solubility of the therapeutic agent(s) in the solvent S1 being 10g/l or higher at 20°C, and a solvent for the one or more polymers, with a solubility of the polymer(s)in the solvent S1 being 100g/l or higher at 20°C, and (ii) at least one solvent S2 which is fully miscible with solvent S1 and which is partially miscible with water, with a solubility of the solvent S2 in water being 1 to 60 wt% of the solvent S2 in relation to the total weight of a mixed phase containing water and the solvent S2 at 20°C; (i) at least one solvent S1 which is fully miscible with water, and which is a solvent for the one or more therapeutic agents with a solubility of the therapeutic agent(s) in the solvent S1 being 10g/l or higher at 20°C, and a solvent for the one or more polymers, with a solubility of the polymer(s)in the solvent S1 being 100g/l or higher at 20°C, and (ii) at least one solvent S2 which is fully miscible with solvent S1 and which is partially miscible with water, with a solubility of the solvent S2 in water being 1 to 60 wt% of the solvent S2 in relation to the total weight of a mixed phase containing water and the solvent S2 at 20°C; b) adding an aqueous surfactant solution with a volume of at least 2 times the volume of the solution provided in step a) to the solution provided in step a) while the solution provided in step a) is stirred, and c) allowing the nano- and/or microparticles to form via extraction of the solvents S1 and S2 into the aqueous surfactant solution.