A pharmaceutical dosage form and method of using same, the pharmaceutical dosage form exhibiting a breaking strength of at least 500 N, said dosage form containing a pharmacologically active ingredient (A); a physiologically acceptable polymer (B) obtainable by polymerization of a monomer composition comprising an ethylenically unsaturated monomer bearing an anionic functional group, in protonated form or a physiologically acceptable salt thereof; a polyalkylene oxide (C) having a weight average molecular weight of at least 200,000 g/mol, wherein the content of the polyalkylene oxide (C) is at least 20 wt.-%, based on the total weight of the dosage form; wherein the pharmacologically active ingredient (A) is present in a controlled-release matrix comprising the polymer (B) and the polyalkylene oxide (C).