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)； an anionic polysaccharide (B) obtainable by introducing anionic functional groups, in protonated form or a physiologically acceptable salt thereof, into a polysaccharide； and a polyalkylene oxide (C)； wherein the pharmacologically active ingredient (A) is present in a controlled-release matrix comprising the anionic polysaccharide (B) and the polyalkylene oxide (C).
