Studies On Pharmacodynamics In Vitro, Pharmacokinetics And Residues Of Florfenicol In Ictalurus Punctatus

In this paper, The vitro antibacterial activity of florfenicol against aquatic pathogenic bacteria, The susceptibility test against aquatic pathogenic bacteria, The drug resistance of aquatic pathogenic bacteria against floffenicol were researched; Acute toxicity of floffenicol to channel catfish(Ictalurus punctures) was investigated; A capillary gas chromatography with electron capture detection method was developed for simultaneous determining the residues of chloramphenicol, floffenicol and thiamphenicol in fish muscule; A high performance liquid chromatographic (HPLC) with UV detection method for the simultaneous determination of residues of floffenicol and its metabolite florfenicol amine in channel catfish (Ictalurus punctatus) plasma, muscule and skin has been established; A high-performance liquid chromatography with flouorescence detection method was studied for simultaneous determination of florfenicol (FF) and florfenicol amine (FFA) in fish muscale; Studies on pharmacokinetics and tissue residues of florfenicol in channel catfish (lctalurus punctatus) at two water temperatures.1. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration on (MBC) of florfenicol against seven kinds of aquatic pathogenic bacteria, The susceptibility test of florfenicol and other twenty four antimicrobial agents against seven kinds of aquatic pathogenic bacteria, and The drug resistance of seven kinds of aquatic pathogenic bacteria against florfenicol. The results showed that floffenicol is effective on aqautic bacteria and aquatic bacteria aren't easy to produce drug resistance.2. The acute toxicity of florfenicol to channel catfish (Ictalurus punctatus) was experimented. The results showed that Florfenicol was taken orally at the does of 1～5g/kg body weight. After 96h, any obvious toxic symptoms or death didn't occur. Again continuously observes 72h, each experimental group fish still did not have obviously toxic symptoms, Living specimen were dissected, internal organs various organs not obvious poison symptom. The LDs0 of florfenicol on Channel catfish (lctalurus punctatus) is bigger than 5g/kg. It suggested that oral florfenicol whith large dose is safe for channel catfish (Ictalurus punctams).3. A capillary gas chromatography with electron capture detection method was developed for determining the residues of chloramphenicol (CAP), florfenicol (FF), and thiamphenicol (TAP) in fish muscule. The standard curves were linear in the investigated ranges, 1.0-500.0μg/L of chloramphenicol and 5.0-500.0μg/L of florfenicol and thiamphenicol.Thc correlation coefficient r≥0.9983.The recoveries were 83.30%～101.22% at spiking levels 0.2-10.0μg/kg. The relative standard deviations were 1.36～12.57%. The detection limit of chloramphenicol, florfenicol, and thiamphenicol were 0.1, 0.2, 0.2μg/kg respectively. It is suitable for simultaneous determination of residues of chloramphenicol, florfenicol and thiamphenicol in aqautic products.4. A high performance liquid chromatographic (HPLC) with UV detection method for the simultaneous determination of residues of florfenicol (FF) and its metabolite florfenicol amine (FFA) in channel catfish plasma and tissues has been established. Phosphate buffer solution was added in channel catfish plasma and tissues. The standard curves were linear in the investigated ranges, 0.01～10.00 mg/L of both florfenicol and florfenicol amine. The correlation coefficient for florfenicol and florfenicol amine were both r=0.9997. The recovery of florfenicol was from 75.14% to 92.65% and the recovery of florfenicol amine was from 76.00% to 91.50%. The relative standard deviations were from 0.41% to 9.30%. The detection limits for florfenicol and florfenicol amine were 25 and 20μg/L, 20 and 15μg/kg, 50 and 50μg/kg, 50 and 50μg/kg, 50 and 50μg/kg respectively in plasma, muscule, skin, liver, and kindey. It is siutable for conducting pharmacokinetics of florfenicol and residues determination of florfenicol and its metabolite florfenicol amine on fish.5. A high-performance liquid chromatography with fluorescence detection method was studied for simultaneous determination of florfenicol (FF) and florfenicol amine (FFA) in fish muscule. The standard curves were linear in the investigated ranges, 10～10000ng/mL of florfenicol and 2-2000ng/mL of florfenicol amine. The correlation coefficient for florfenicol was r=l and r=0.9999, respectively. At the florfenicol and florfenieol amine spiked level 20～200μg/kg and 4-50μg/kg. The recoveries were 79.26%～90.63%. The relative standard deviations were from 3.66%～6.21%. The detection limits for florfenicol and florfenicol amine were 5μg/kg and 1μg/kg. The results showed that the method is sensitive, simple, accurace, rapid, particular for the simultaneous determination florfenicol and florfenicol amine in fishry products.6. A pharmacokinetics and residues study of florfenicol (FF) was investigated after oral gavage administration in channel catfish (Ictalurus punctatus) at 18℃and 28℃water temperature. Florfenicol concentrations in plasma and florfenicol and its metabolite florfenicol amine concentrations in tissue were determined using hingh-perfomance liquid chromatography (HPLC) with UV detection. Pharmacokinetic parameters were calculated by using the 3p97 (Practical Pharmacokinetic Program) software (Mathematics Special Field Committee Chinese pharmacology institute, China). The kinetic of the drug was found to be temperature independent. Plasma concetration-time data of florfenicol were best fitted using a one-compartmental open model at 18℃and 28℃water temperature. The kinetic equation were C_plasma=7.92(e^0.036t-e^-0.18t) and C_plasma=9.06(e^-0.08lt-e(-0.30t) respectively at 18℃and 28℃. With the rise of water temperature, the speed of absorption, distribution and elimination of FF in plasma accelerated, T_1/2ka of the 28℃group was about three fifth, T_1/2ke, MRT and AUC were about half than those of the 18℃group, but the relatively apparent distribution volume V/F_(c) were approached. After continual oral garages administration for 3 days at a dose of 10mg/kg body weight, FF and its metabolite FFA were simultaneously detected in muscule, skin, liver, and kindey at 1, 2, 3, 5, 7, and 9days. The sum of FF and FFA is taken marker residue. The results revealed that the depletion of the marker residue in channel catfish (Ictalurus punctatus) is faster at higher water temperature. To compare with other tissues, the elimination of the marker residue in kindy was slowest, Kindey was the main reservoir of the marker residue in channel catfish (Ictalurus punctatus). It is proposed that withdrawl time were 13d and 8d respectively at 18℃and 28℃, According to the maximum residue limit (MRL) of the marker residue of 300μg/kg in kindey. The reliable theory basis to make dosage regimen and withdrawl time at different water temperature based on the study.