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The pharmacokinetics of florfenicol and its metabolite, florfenicol amine, was investigated after its intravenous (i.v.) and oral (p.o.) administration of 20 mg/kg of body weight in Korean catfish (Silurus asotus). After i.v. florfenicol injection (as a bolus), the terminal half-life (t(1/2)), the volume of distribution at steady state (V(dss)), and total body clearance were 11.12 +/- 1.06 h, 1.09 +/- 0.09 L/kg and 0.07 +/- 0.01 L x kg/h respectively. After p.o. administration of florfenicol, the t(1/2), C(max), t(max) and oral bioavailability (F) were 15.69 +/- 2.59 h, 9.59 +/- 0.36 microg/mL, 8 h and 92.61 +/- 10.1% respectively. Florfenicol amine, an active metabolite of florfenicol, was detected in all fish. After i.v. and p.o. administration of florfenicol, the observed C(max) values of florfenicol amine (3.91 +/- 0.69 and 3.57 +/- 0.65 mg/L) were reached at 0.5 and 7.33 +/- 1.15 h. The mean metabolic rate of florfenicol amine after i.v. and p.o. administration was 0.4 and 0.5 respectively.

The objective of this study was to evaluate the pharmacokinetic profile of enrofloxacin and its active metabolite, ciprofloxacin, in Korean catfish after intravenous and oral administrations. Enrofloxacin was administered to Korean catfish by a single intravenous and oral administrations at the dose of 10 mg/kg body weight. The plasma concentrations from intravenous and oral administrations of enrofloxacin were determined by LC/MS. Pharmacokinetic parameters from both routes were described to have a two-compartmental model. After intravenous and oral administrations of enrofloxacin, the elimination half-lives (t(1/2,beta)), area under the drug concentration-time curves (AUC), oral bioavailability (F) were 17.44 +/- 4.66 h and 34.13 +/- 11.50 h, 48.1 +/- 15.7 microgxh/mL and 27.3 +/- 12.4 microgxh/mL, and 64.59 +/- 4.58% respectively. The 3.44 +/- 0.81 h maximum concentration (C(max)) of 1.2 +/- 0.2 microg/mL. Ciprofloxacin, an active metabolite of enrofloxacin, was detected at all the determined time-points from 0.25 to 72 h, with the C(max) of 0.17 +/- 0.08 microg/mL for intravenous dose. After oral administration, ciprofloxacin was detected at all the time-points except 0.25 h, with the C(max) of 0.03 +/- 0.01 microg/mL at 6.67 +/- 2.31 h. Ciprofloxacin was eliminated with terminal half-life t(1/2,beta) of 52.08 +/- 17.34 h for intravenous administration and 52.43 +/- 22.37 h for oral administration.

The pharmacokinetics of florfenicol and its active metabolite florfenicol amine were investigated in rabbits after a single intravenous (i.v.) and oral (p.o.) administration of florfenicol at 20 mg/kg bodyweight. The plasma concentrations of florfenicol and florfenicol amine were determined simultaneously by an LC/MS method. After i.v. injection, the terminal half-life (t(1/2lambdaz)), steady-state volume of distribution, total body clearance and mean residence time of florfenicol were 0.90 +/- 0.20 h, 0.94 +/- 0.19 L/kg, 0.63 +/- 0.06 L/h/kg and 1.50 +/- 0.34 h respectively. The peak concentrations (C(max)) of florfenicol (7.96 +/- 2.75 microg/mL) after p.o. administration were observed at 0.90 +/- 0.38 h. The t(1/2lambdaz) and p.o. bioavailability of florfenicol were 1.42 +/- 0.56 h and 76.23 +/- 12.02% respectively. Florfenicol amine was detected in all rabbits after i.v. and p.o. administration. After i.v. and p.o. administration of florfenicol, the observed Cmax values of florfenicol amine (5.06 +/- 1.79 and 3.38 +/- 0.97 microg/mL) were reached at 0.88 +/- 0.78 and 2.10 +/- 1.08 h respectively. Florfenicol amine was eliminated with an elimination half-life of 1.84 +/- 0.17 and 2.35 +/- 0.94 h after i.v. and p.o. administration respectively.

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