This paper describes the development of analytical methods for the quantification of albendazole (ABZ) in fish feed and ABZ and its main known metabolites (albendazole sulfoxide, albendazole sulfone and albendazole aminosulfone) in fish fillet employing LC-MS/MS. In order to assess the reliability of the analytical methods, evaluation was undertaken as recommended by related guides proposed by the Brazilian Ministry of Agriculture for analytical method validation. The calibration curve for ABZ quantification in feed showed adequate linearity (r > 0.99), precision (CV < 1.03%) and trueness ranging from 99% to 101%. The method for ABZ residues in fish fillet involving the QuEChERS technique for sample extraction had adequate linearity (r > 0.99) for all analytes, precision (CV < 13%) and trueness around 100%, with CCα < 122 ng g and CCβ < 145 ng g. Besides, by aiming to avoid the risk of ABZ leaching from feed into the aquatic environment during fish medication via the oral route, a promising procedure for drug incorporation in the feed involving coating feed pellets with ethyl cellulose polymer containing ABZ was also evaluated. The medicated feed had good homogeneity (CV < 3%) and a lower release of ABZ (< 0.2%) from feed to water when the medicated feed stayed in the water for up to 15 min.

Few drugs are specifically regulated for aquaculture. Thus this study considered albendazole (ABZ) as a potential drug for use in fish, which, however, is not yet regulated for this application. ABZ is a broad-spectrum anthelmintic approved for farmed ruminants and recently considered for treatment of fish parasites. It is the subject of careful monitoring because of potential residues in animal products. This study evaluated the depletion of ABZ and its main known metabolites: albendazole sulfoxide - ABZSO, albendazole sulfone - ABZSO and albendazole amino sulfone - ABZ-2-NHSO, in the fillets of the Neotropical Characin pacu, Piaractus mesopotamicus, which were fed diets containing 10 mg ABZ kg body weight in a single dose. Fish were euthanised at 8, 12, 24, 48, 72, 96 and 120 hours after medication and the depletion profiles of ABZ, each metabolite and the sum of all marker residues were assessed and evaluated taking into account methodological variations regarding determination of the maximum residue limits adopted by different international regulating agencies for estimation of the withdrawal period (WP). The estimated WPs ranged from 2 to 7 days.

Agradeço a Deus pelo amor incondicional, pela vida, pela minha família e pelas oportunidades que tem me proporcionado. Aos meus pais, Luiz e Zenaide, por terem lutado para que eu pudesse estudar, por sempre estarem presentes na minha vida, por terem me apoiado na minha escolha profissional, por terem me ajudado e me orientado em todos os momentos. Ao meu irmão, Ítalo, por estar sempre comigo e por ter me ajudado inúmeras vezes. Ao Lucas pelo amor, apoio e compreensão. Obrigado por estar comigo nos momentos perfeitos e nas horas difíceis. Você é muito importante para mim. Ao meu orientador, Prof. Dr. Jonas A. R. Paschoal, pelo aceite em me orientar, pelo apoio durante todo o desenvolvimento deste trabalho, pela paciência, pelo incentivo e por contribuir de maneira imensurável na minha formação acadêmica. Muito obrigada! Ao Prof. Dr. Oswaldo de Freitas pelo auxílio no desenvolvimento da ração. Aos amigos de laboratório, Marina, Rodolfo, Ana Paula, Juliana, Pedro, Carol pelos bons momentos, ajuda, troca de experiências, discussões e conhecimentos. Aos colegas funcionários do laboratório, Roberto e Agnaldo pela amizade e suporte para a execução deste projeto.