Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This work evaluated the degradation of ivermectin, a veterinary drug widely used in the treatment of ectoparasites and endoparasites, and the removal of acute toxicity (using Daphnia similis) by Fenton (Fe2+/H2O2) and photo-Fenton (Fe2+/H2O2/UV) processes. Fe2+ and hydrogen peroxide concentrations ranged from 0.25 to 1.0 mmol L-1 and from 0.5 to 10.0 mmol L-1, respectively. With Fenton's reagent, it was possible to reach 90% degradation efficiency in 600 s, while the photo-Fenton resulted in 99% for the same reaction time. Both processes achieved higher degradation rates in the first 60 seconds and the toxicity decreased along the reaction time. The photo-Fenton process was more efficient in reducing the drug concentration and the solution toxicity.142292301Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [08/06470-0]