Depletion study and estimation of the withdrawal period for oxytetracycline in tilapia cultured in Brazil
Article first published online: 6 APR 2011
© 2011 Blackwell Publishing Ltd
Journal of Veterinary Pharmacology and Therapeutics
Volume 35, Issue 1, pages 90–96, February 2012
How to Cite
PASCHOAL, J. A. R., BICUDO, Á. J. A., CYRINO, J. E. P., REYES, F. G. R. and RATH, S. (2012), Depletion study and estimation of the withdrawal period for oxytetracycline in tilapia cultured in Brazil. Journal of Veterinary Pharmacology and Therapeutics, 35: 90–96. doi: 10.1111/j.1365-2885.2011.01294.x
- Issue published online: 6 JAN 2012
- Article first published online: 6 APR 2011
- (Paper received 26 January 2011; accepted for publication 24 February 2011)
Paschoal, J. A. R., Bicudo, Á. J. A., Cyrino, J. E. P., Reyes, F. G. R., Rath, S. Depletion study and estimation of the withdrawal period for oxytetracycline in tilapia cultured in Brazil. J. vet. Pharmacol. Therap. 35, 90–96.
Defining pharmacokinetic parameters and depletion intervals for antimicrobials used in fish represents important guidelines for future regulation by Brazilian agencies of the use of these substances in fish farming. This article presents a depletion study for oxytetracycline (OTC) in tilapias (Orechromis niloticus) farmed under tropical conditions during the winter season. High performance liquid chromatography, with fluorescence detection for the quantitation of OTC in tilapia fillets and medicated feed, was developed and validated. The depletion study with fish was carried out under monitored environmental conditions. OTC was administered in the feed for five consecutive days at daily dosages of 80 mg/kg body weight. Groups of ten fish were slaughtered at 1, 2, 3, 4, 5, 8, 10, 15, 20, and 25 days after medication. After the 8th day posttreatment, OTC concentrations in the tilapia fillets were below the limit of quantitation (13 ng/g) of the method. Linear regression of the mathematical model of data analysis presented a coefficient of 0.9962. The elimination half-life for OTC in tilapia fillet and the withdrawal period were 1.65 and 6 days, respectively, considering a percentile of 99% with 95% of confidence and a maximum residue limit of 100 ng/g. Even though the study was carried out in the winter under practical conditions where water temperature varied, the results obtained are similar to others from studies conducted under controlled temperature.