The invention relates to a process for producing a coated drug form or a drug form in the form of an active ingredient matrix, by processing a copolymer, an active pharmaceutical ingredient, a core if present and/or pharmaceutically customary excipients in a conventional manner by melting, injection molding, extrusion, wet granulation, casting, dipping, spreading, spraying or compression to form a coated drug form and/or to form an active ingredient matrix, characterized in that a copolymer is used which is composed of 20 to 33% by weight methacrylic acid, 5 to 30% by weight methyl acrylate, 20 to 40% by weight ethyl acrylate and more than 10 to 30% by weight butyl methacrylate and, if desired, 0 to 10% by weight further vinylically copolymerizable monomers, with the proviso that the glass transition temperature of the copolymer in accordance with ISO 11357-2, section 3.3.3, is 55 to 70.degree. C. The invention further relates to the drug form produced in accordance with the invention, to the copolymer, and to the use thereof.