| The main active ingredient of tilmicosin phosphate is tilmicosin. The water solubility of tilmicosin phosphate is good, and easy to be developed into the drinking preparation, which is convenient for Clinical Drug Administration. At present, there are few reports on antimicrobial activity, clinical pharmacodynamics, pharmacokinetics and residue dynamics of tilmicosin phosphate and its preparation. For this reason, this study focus on the clinical field trial and the residues elimination of tilmicosin phosphate in chickens. The research not only confirmed the dosage regimen for clinical usage and provided residue’s surveillance but also gave the the basis for the formulation of withdrawal period which means a lot for the rational clinical use of drug.1. The clinical field trial of 10% Tilmicosin phosphate soluble powder in treating chickens infected by mycoplasma gallisepticumTo further confirm the dosage of tilmicosin phosphate soluble powder in treating respiratory tract infection of chicken caused by mycoplasma based on the early susceptibility test and dose screening test, chickens which diagnosed mycoplasma gallisepticam infection were divided into two groups. Chickens in group one were treated with 10% tilmicosin phosphate soluble powder at recommended dogage while in group two were with 10% tilmicosin soluble powder at recommended dosage. According to usually clinical observation、morbidity、 cure rates、effective rate and mortality examination, the 10% tilmicosin phosphate soluble powder and 10% tilmicosin soluble powder have similar efficacy on respiratory tract infection.2. Determination of Tilmicosin residue in chicken edible tissues by high performance liquid chromatographyA HPLC external standard method was developed for determining residues of tilmicosin phosphate in chicken edible tissues. Tilmicosin phosphate in edible tissues of chickens were extracted with acetonitrile and cleaned up by Bond Elut SPE C18 cartridges. Acetonitrile. tetrahydrofuran, Dibutyl amine phosphate buffer and water (10.5:5:5:79.5. V/V/V/V) were used as the mobile phase. The mean recoveries of tilmicosin fortified at 0.05、0.50'5.00μg/g in chickens tissues were within the range of 80%-100%. The limit of detection (LOD) and the limit of quantification(LOQ) in edible tissues of chickens were 0.025 μg/g and 0.05 μg/g respectively. The validated HPLC assay method is suitable for the detection of the tilmicosin residual amount of muscle, liver, kidney and skin+fat in chickens.3. Residue elimination of 10% Tilmicosin Phosphate soluble powder and withdrawal period determination in chickensThirty health yellow-feathered broilers weighting 1.5-2kg were offered with 75mg/L tilmicosin phosphate soluble powder in drinking water for 3 successive days. The chickens were sacrificed on 2d、5d、8d、1 d and 14 d after the last administration. Concentrations of tilmicosin in samples of edible tissues were determined using the above validated HPLC assay. The result showed, after 13 days withdrawal, the residues in all edible tissues were above MRL. The concentration of tilmicosin was highest in liver after 5 days withdrawal (1.4288±0.6707 mg/kg), and then in kidney(20.6125±0.2128 mg/kg), the concentration in muscle and skin+fat were lowest in all collected tissues(0.0892±0.0500 mg/kg and 0.0328±0.0082 mg/kg). after 8 days withdrawal, the residues in liver、skin+fat and muscle were below MRL. Besides that, the concentration in kidney from one chicken was above MRL, the residues in kidney were 0.1502± 0.1217 mg/kg. At 11 d after injection, the residues in liver from one chicken was above MRL. after 13 days withdrawal, the residues in all edible tissues were below MRL. which indicated that the kidney and liver ware the target organs of residue surveillance. The raw data were analyzed with WT1.4 withdrawal period program. The withdrawal period was 11.70 d in liver、 12.53 d in kidney. Depending on the measured value of tilmicosin residure, withdrawal period was estimated to be 8 days in fat and muscle tissue. In the conclusion, the withdrawal period was 13 days for 10% tilmicosin phosphate soluble powder when chickens were administrated with the recommended dosage. |
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