Pharmacokinetics Of Ceftiofur Sodium In Grass Carp, Ctenopharyngodon idella     Amornchai Somjetlertcharoen and Stephen A. Smith   Aquatic Medicine Laboratory, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0442     Ceftiofur sodium, a third generation cephalosporin, was administered to grass carp (Ctenopharyngodon idella) by four different routes: intracardiac (IC), intraperitoneal (IP), intramuscular (IM) and oral (PO) administration at a single dosage of 8 mg/kg body weight. Serial blood samples were obtained and plasma samples were analyzed by high performance liquid chromatography for ceftiofur (as measured by its metabolite, desfuroylceftiofur (DFC) and DFC-related metabolite concentrations). Disposition pharmacokinetic data were best described by a two compartment open model for IC and non-compartment model with no lag time for IP and IM administrations. Oral absorption of ceftiofur was not observed in this species. Following IC, IP and IM ceftiofur sodium administration, the final elimination half-lives, maximum plasma concentration, time to reach maximum concentration, volume of distribution and plasma clearance were 0.38, 0.45 and 13.15 hours; 157.09, 31.54 and 8.86 μg/ml; 0, 0.25 and 0.5 hours; 0.09, 0.17, 0.63 l/kg; and 0.21, 0.26, 0.03 ml/min/kg, respectively.