The invention relates to a thermoformed pharmaceutical dosage form having a breaking strength of at least 300 N, said dosage form comprising- a pharmacologically active ingredient (A),- a free physiologically acceptable acid (B) in an amount of from 0.001 wt.-% to 5.0 wt.-%, based on the total weight of the pharmaceutical dosage form, and- a polyalkylene oxide (C) having a weight average molecular weight Mw of at least 200,000 g/mol.
