RESIDUE DEPLETION STUDIES ON DANOFLOXACIN IN THE CHICKEN

Penetration of danofloxacin into tissues is consistent-with oral bioav ailability and pharmacokinetic plasma data derived from chickens given danofloxacin by iv bolus and oral gavage administration at 5 mg/kg. T his pharmacokinetic assessment was confirmed when [H-3]danofloxacin wa s administered to broilers in drinking water at 25 mu g/mL for 5 days, and tissues were assayed for residues. Under this regimen, total resi dues of danofloxacin were higher in liver than other tissues and decli ned in liver from 0.612 mu g/g at 6 h to 0.056 mu g/g by 48 h of withd rawal, suggesting rapid depletion. In kidney and muscle total residues depleted in parallel with liver but were 2- and 10-fold lower, respec tively. The major residue in all tissues was unchanged danofloxacin. A n N-demethyl metabolite was found in liver and excreta but was not det ected in muscle or fat/skin, indicating that it is an excretory metabo lite. The depletion of unchanged and N-demethyl metabolite residues fr om edible tissues of the chicken was confirmed by HPLC with fluorescen ce detection when danofloxacin was given to 3-week-old chickens under a commercial use condition, i.e., in drinking water for 3 days at 5 mg /kg of body weight per day.