Residue Depletion Study of Danofloxacin in Cultured Tilapia (Oreochromis mossambicus).

Danofloxacin is an antibacterial drug of the fluoroquinolone group developed for therapeutic purposes in veterinary medicine. The studies described here include investigations of the residues following a single dose or multiple doses of danofloxacin. Residue depletion studies were performed to determine residues in plasma and tissues of saltwater tilapia fish (Oreochromis mossambicus) after a single oral administration of danofloxacin at the dose of 10 mg/kg body weight and also after daily dose of 10 mg/kg body weight for five consecutive days. Danofloxacin residues were analyzed by HPLC with fluorescence detection. Following a single oral dose, danofloxacin residues in 6 h postdosing tilapia were at a maximum of 1.44, 1248, and 13.18 mu g/g in serum, liver, and kidney samples, respectively, while a peak muscle concentration of 2.15 mu g/g was reached at 12 h. From single-dose data, the concentration of danofloxacin in serum, muscle, liver, and kidney samples declined with half-lives of 29, 34, 49, and 44 h, respectively. Based on the maximum residue level (MRL) of 0.1 mu g/g in edible tissue for fin fish, the withdrawal times of danofloxacin in muscle were estimated to fall below the MRL after a withdrawal period of 21 days following the multiple-dose administration. These results may be helpful to regulatory agencies as they determine what tissues should be monitored to ensure that the established residue safety tolerance levels are not exceeded.