| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 95 === Florfenicol (Ff) is a synthetic antibiotic with broad antibacterial spectrum and high therapeutic effectiveness that was specially developed for veterinary use. The pharmacokinetic disposition of Ff in chickens has only been scarcely reported. Therefore, in the present study, we described a microdialysis model designed for fowl species to monitor Ff concentration in peripheral tissues (femoral and pectoral muscles) and compared them to the pharmacokinetics of Ff in the blood of chickens. Leghorn chickens and natural broilers (n=18 each) were given single oral dose of Ff (30 mg/kg). Plasma samples were collected from the two breeds of chickens (n=5 each) and tissue dialysates were collected at preset intervals from the Leghorn chickens (n=5). All the chickens were also divide into twelve group and slaughtered at 12, 24, 36 48, 60 and 72 hr after the administration. The samples were analyzed by a HPLC-UV method. The results for pharmacokinetic studies showed that the oral pharmacokinetics of Ff in chickens was best fitted to a two-compartment open model. The elimination half-lives (t1/2) of Leghorn chickens and natural broilers were 181.85 and 98.09 min and the total body clearance (Cltot) were 0.72 and 1.26 L/hr/kg, respectively. Ff was more quickly absorbed with a relatively shorter t1/2 in natural broilers than in Leghorn chickens. No residues of Ff were detected in tissues at 72 hr after the last dose. In Leghorn chickens, the t1/2 of pectoral and femoral muscles by microdialysis were 105.54 and 109.84 min, respectively. The peak concentrations in pectoral and femoral muscles were also lower than that in the plasma. When the two muscle sites were compared, femoral muscle exhibited higher peak concentration and reached the peak 10 minutes earlier than in the pectoral muscle. Results from this investigation demonstrated the practicality of using in vivo microdialysis in chickens and have revealed significant time-dependent differences in the free concentrations and pharmacokinetics of Ff in muscles and in the blood. This approach should be readily adaptable for use in other fowl species and could improve our understanding of clinical pharmacokinetics for effective therapy as well as the capacity to estimate drug residues in specific tissues of interest.
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