The electrochemical detection and electrooxidation path of the first-generation antihistamine receptor hydroxyzine (HDZ) and its main metabolite cetirizine (CTZ) are addressed in this research. A carbon black-modified electrode to explore the electrochemical responsivity and electroanalytical detection of HDZ and CTZ was designed. Compared to the bare electrode, the irreversible anodic responses observed for HDZ and CTZ were considerably improved on the proposed carbon black-modified electrode, including twenty times enhancement of the anodic peak currents and the shifting of anodic peak potentials to less positive potentials. In order to identify the electrooxidation products resulting from the previously verified irreversible redox processes, cyclic voltammetric studies and potentiostatic electrolysis assays followed by products identification by nuclear magnetic resonance (NMR) spectroscopy were carried out. From the combination of electrochemistry and NMR spectroscopy data it was possible to propose electrooxidation reaction mechanisms for HDZ and CTZ molecules. By applying square-wave adsorptive anodic stripping voltammetry (SWAdASV) under optimized experimental conditions, the obtained analytical curves for HDZ and CTZ were linear from 2.99 x 10(-7) to 9.81 x 10(-6) mol L-1 and from 4.97 x 10(-7) to 1.08 x 10(-5) mol L-1, with limits of detection of 1.00 x 10(-7) mol L-1 and 4.00 x 10(-7) mot L-1, respectively. Finally, spiked synthetic human biological fluids were analysed by the proposed SWAdASV procedures, with recovery percentages close to 100%.