In doping controls it is important to exclude essential substances that are not in the list of forbidden drugs. Similarly it is important as well for these drugs to be proved in analgesic mixture abuse. An example being the proof of amidopyrine and its metabolites, further on p-phenetidine as a metabolie of phenacetin in alkaline urine extracts. Results are given in using thin-layer chromatography, gas chromatography and the identification by means of gas chromatography/mass spectrometry.