Depletion study and estimation of the withdrawal period for enrofloxacin in pacu (Piaractus mesopotamicus)

Defining the pharmacokinetic parameters and depletion intervals for antimicrobials used in fish will help in the development of important guidelines for future regulations by Brazilian agencies on the use of these substances in fish farming. This paper presents a depletion study for enrofloxacin (ENR) and its main metabolite, ciprofloxacin (CIP), in pacu (Piaractus mesopotamicus) fillets. The depletion study was carried out under monitored environmental conditions, with the temperature controlled at 27 degrees C to mimic the fish farming conditions in Brazil. ENR was administered orally via medicated feed for 10 consecutive days at daily dosages of 10mg/kg body weight (b.w.). The fish were slaughtered at 6, 12, and 24h and 2, 3, 5, 8, 12, 17, and 24days after the medication period. Considering a maximum residue limit of 100g/kg for the sum of the ENR and CIP residues in the fillet, the results obtained in the depletion study allowed the estimation of a half-life for ENR of 2.75days and a withdrawal period of 23days. The results obtained in this study are important for the farming of pacu in tropical regions.