The invention relates to a pharmaceutical dosage form having a breaking strength of at least 300 N, said dosage form comprising -an opioid (A) selected from the group consisting of Oxymorphone, Oxycodone, Tapentadol, Hydromorphone, Hydrocodone, Morphine, and the physiologically acceptable salts thereof wherein the weight content of the opioid (A) is within the range of from 5.0 to 35 wt.-%, based on the total weight of the pharmaceutical dosage form -an anionic polysaccharide (B) selected from the group consisting of croscarmellose, carmellose, crosslinked carboxymethyl starch, carboxymethyl starch, and the physiologically acceptable salts thereof wherein the weight content of the anionic polysaccharide (B) is within the range of from 5.0 to 35 wt.-%, based on the total weight of the pharmaceutical dosage form and -a polyalkylene oxide (C) having a weight average molecular weight of at least 200,000 g/mol wherein the weight content of the polyalkylene oxide (C) is within the range of from 20 to 80 wt.-%, based on the total weight of the pharmaceutical dosage form wherein the opioid (A) is present in a controlled-release matrix comprising the anionic polysaccharide (B) and the polyalkylene oxide (C).
