Real-time monitoring of the electrochemical degradation of acetaminophen was performed using a biomimetic sensor coupled to a flow injection analysis (FIA) system. Degradation of the drug was carried out at constant current density (24 to 180mAcm-2) in an electrolyte consisting of 0.1molL-1 K2SO4/5.0×10-4molL-1 FeSO4·7H2O. Two commercial DSA anodes (DSA-Cl2 and DSA-O2) were compared. The degradation process was monitored on-line using an amperometric sensor based on the biomimetic catalyst iron(III) tetrapyridinoporphyrazine (FeTPyPz), coupled to the degradation cell. The optimized FIA detection system employed the electrolyte solution as carrier, a flow rate of 1.25mLmin-1 and an injected sample volume of 75μL. The real-time data obtained showed, as expected, that acetaminophen degradation followed pseudo-first order kinetics, with the DSA-Cl2 anode showing a higher efficiency according to the calculated apparent rate constant values. The advantage of the proposed on-line system is that a larger number of points can be monitored in a shorter time compared to other off-line methods, which improves the accuracy of estimates of electrochemical degradation constants. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.