A pharmaceutical dosage form exhibiting a breaking strength of at least 500 N, wherein the dosage form contains a pharmacologically active ingredient (A); an inorganic salt (B); and 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 inorganic salt (B) and the polyalkylene oxide (C) and wherein, under in vitro conditions, the release profile of the pharmacologically active ingredient (A) from the matrix comprises at least a time interval during which the release follows zero order kinetics.