Pharmacokinetics And Residues Of Thiamphenicol In Crucian Carp At Different Temperatures

Pharmacokinetics and residues elimination of thiamphenicol (TAP) were studied in crucian carp (Carassius auratus) kept at two water temperatures of10and25℃. TAP concentrations in plasma and tissues were analyzed by means of reversed-phase high-performance liquid chromatography (RP-HPLC) after liquid-liquid extraction. The correlation of calibration curves were all good, which correlation coeffcients (r) were more than0.9996. The average extraction recoveries were more than87%from plasma, more than74%from skin, muscle, liver and kidney. The intra-day and inter-day coefficients of variation were less than7%and9%, respectively.Fish were administered orally with a single dosage of15mg/kg body weight in the pharmacokinetics group. The results showed that the pharmacokinetic characteristics of TAP in crucian carp manifested a slow absorption, wide distribution and slow elimination. Water temperature played an important role in the kinesics process. The plasma concentration-time datas conformed to one-compartment open models at both temperatures. The absorption half-lives (t1/2ka) of TAP were found to be4.63and2.72hat10and25℃. respectively, and the elimination half-lives (t1/2β) were13.68and9.87h at10and25℃. The peak plasma concentration (Cmax) were calculated as5.71μg/mL at10℃and5.60μg/mL at25℃. and the time to reach the peak (Tmax)were figured out at10.94h at10℃and6.98h at25℃, respectively. The distribution volumes (Vd/F) of TAP were computed to be1.36L/kg at15℃and0.87L/kg at25℃. The total clearances of TAP (CLb) were estimated as0.08and0.12L/(h·kg) at10and25℃, respectively. The areas under the concentration-time curve (AUC) were195.99μg·h/mL at10℃and130.16μg-h/mL at25℃.After repeated oral administration with a dosage of15mg/kg body weight per day for3days, fish were killed at1,3,5,7,13,18,24,36,48and72h after the last administration and the samples of muscle, skin, liver and kidney were gathered to determine TAP concentrations. The results showed that the elimination half-lives (t1/2β) of TAP from all tissues at10℃were obviously slower than those at25℃. The drug could still be detected at72h time-point after the last administration in most tissues at lower and higher temperatures, except for the liver at25℃. Comparing with other tissues, the concentrations of TAP were higher in skin at most time-points. At the same time, the eliminations in skin were slower than those in other tissues In order to facilitate, the elimination of TAP in skin could be behaved as a reservoir in crucian carp.Based on the results of the residue study, if fish were administered TAP orally with a single dosage of15mg/kg body weight for some days, the withdrawal periods should not be less than10d at10℃and6d at25℃.