PHARMACOKINETICS OF OXYTETRACYCLINE IN THE RED PACU (COLOSSOMA-BRACHYPOMUM) FOLLOWING DIFFERENT ROUTES OF ADMINISTRATION

Oxytetracycline (OTC) pharmacokinetics were studied in the red pacu (C olossoma brachypomum) following intravenous (i.v.) and intramuscular ( i.m.) administration at a dose of 5 mg/kg body weight, OTC plasma conc entrations were determined by high-performance-liquid-chromatography ( HPLC). A non-compartmental model was used to describe plasma drug disp osition after OTC administration. Following i.m. administration, the e limination half-life (t(1/2)) was 62.65 +/- 1.25 h and the bioavailabi lity was 49.80 +/- 0.01%. After i.v. administration the t(1/2) was 50. 97 +/- 2.99 h, the Vd was 534.11 +/- 38.58 mL/ kg, and CIb was 0.121 /- 0.003 mL/min.kg. The 5 mg/kg i.v. dose used in this experiment resu lted in up to 48 h plasma concentrations of OTC above the reported MIC values for some strains of fish pathogens such as Aeromonas hydrophil a, A. liquefaciens, A. salmonicida, Cytophaga columnaris. Edwardsiella ictaluri, Vibrio anguillarium, V. ordalii, V., salmonicida and Yeersi nia ruckeri. These MIC values are below the susceptible range (4 mu g/ mL) listed by the National Committee for Clinical Laboratory Standards (NCCLS) as determined by the NCCLS susceptibility interpretive criter ia.