盐酸二氟沙星（Difloxacin Hydrochloride）是动物专用氟喹诺酮类药物，具有抗菌谱广、口服吸收迅速、半衰期长、低毒、高效等特点。混悬乳剂能降低药物毒副作用和刺激性，实现靶向、缓释和长效作用。本文对盐酸二氟沙星混悬乳剂注射液的毒理学作用和其在猪可食性组织中的残留作了初步研究，以期为盐酸二氟沙星混悬乳剂在兽医临床上的应用提供理论基础。 1 盐酸二氟沙星混悬乳剂的毒理学研究 为探讨盐酸二氟沙星混悬乳剂对靶动物的毒理学效应及程度，本试验就盐酸二氟沙星混悬乳剂对昆明种小鼠的急性毒性、蓄积毒性、亚慢毒性、致突变作用和生殖发育毒性进行了研究。用改良寇氏法测定LD50；采用剂量递增法计算蓄积系数；连续4周给小鼠腹腔注射盐酸二氟沙星混悬乳剂观察小鼠的亚慢性毒性反应；观察小鼠的精子畸形毒性和微核毒性评价其致突变作用，大鼠的致畸试验评价其生殖发育毒性。结果表明，盐酸二氟沙星混悬乳剂对小鼠口服LD50 =2 303.56 mg/kg，95%可信限为2 120.41 mg/kg～2 502.65 mg/kg；对小鼠腹腔注射LD50 =723.89 mg/kg，95%可信限为678.45 mg/kg～772.37 mg/kg；蓄积试验中小鼠死亡一只，蓄积系数K>5.26，为弱蓄积性且长期染毒会出现耐受现象；亚慢性毒性试验高剂量组（1/5LD50）小鼠在用药后出现精神沉郁、采食量下降、增重缓慢等毒性反应，血液学及血液生化学检查各生理生化指标各组间比较差异不显著，病理组织学检查见高剂量组小鼠肝脏和肾脏有轻微炎症变化；小鼠微核试验和精子畸形试验结果均呈阴性；大鼠致畸试验结果表明：高剂量组（350 mg/kg）明显降低胎鼠存活率，显著影响胚胎的生长发育，其严重程度具有剂量效应关系。盐酸二氟沙星混悬乳剂注射液的急性毒性较小，弱蓄积毒性，无致突变毒性，反复应用盐酸二氟沙星混悬乳剂注射液可以使动物产生耐受性，对SD大鼠有一定的致畸作用。 2盐酸二氟沙星混悬乳剂在猪组织中的残留研究 建立了反相高效液相色谱法测定猪组织中盐酸二氟沙星残留量的方法。采用C18色谱柱（5 μm，250 mm×4.6 mm），称取2.028 g磷酸二氢钠溶于1 000 mL水中，加入10 mL冰乙酸，将此溶液与乙腈按30:70的比例作为流动相，紫外检测波长为280 nm。将盐酸二氟沙星以20、100、500 μg/kg分别添加到空白组织中，测得肌肉、肝脏、肾脏、肺脏、脂肪+皮肤组织中盐酸二氟沙星回收率均在75%以上，平均回收率分别为84.72%、80.17%、76.78%、77.90%、79.61%。日内变异RSD为1.09%～5.96%，日间变异RSD为1.17%～4.97%。该方法的最低检测限为10 μg/kg，在10～1 000 μg/kg范围内时，线性关系良好。以5 mg/kg的剂量单次肌肉注射5%盐酸二氟沙星混悬乳剂，测定不同组织中二氟沙星的浓度。依据我国及欧盟兽药残留标准，建议休药期为32 d。

Difloxacin hydrochloride is one of fluoroquinolones used only for veterinary, and shows a broad spectrum and high performance of antimicrobial activity with low toxicity. It can be rapidly absorbed by oral administration, and has long half-life. Suspension emulsions can achieve the effect of target treatment, sustained release and long-acting, which can reduce the drug toxic , side effects and stimulation. In this article, primary study on the toxicity and residue in pig’s tissues of difloxacin hydrochloride suspension emulsions was performed to provide theoretical foundation for its clinical application in veterinary practice. 1 Study on the toxicity of Difloxacin hydrochloride suspension emulsions In order to research the toxicological effects and extent of difloxacin hydrochloride suspension emulsions to target animals,This experiment was designed to investigate acute toxicity, accumulative toxicity, sub-chronic toxicity, mutagenic toxicity and reproductive and developmental toxicity of difloxacin hydrochloride suspension emulsions injection in mice. Acute toxic effect and accumulative toxic effect of difloxacin hydrochloride suspension emulsions injection were detected by modified Kaber method and accumulation coefficient method respectively. The mice were injected with difloxacin hydrochloride suspension emulsions subsequently for 28 d to evaluate the sub-chronic toxicity. Micronucleus test and sperm structural test of difloxacin hydrochloride suspension emulsions injection were carried out in KM mice to evaluate its mutagenic toxicity. Teratogenicity of SD rats were used for evaluating its reproductive and developmental toxicology. The mouse oral LD50 of difloxacin hydrochloride suspension emulsions injection was 2 303.56 mg/kg and the 95% confidence interval was 2 120.41 to 2 502.65 mg/kg; LD50 arrived at 723.89 mg/kg after intraperitoneal injection of its suspension and 95% confidence interval was 678.45 mg/kg to 772.37 mg/kg. The accumulative coefficient(K) was beyond 5.26 and test group occurred one death. The toxic signs of the mice exposed to high dose that included depression, decreased appetite and poor gain weight in the subchronic toxicity test. The results of blood routine examination and biochemical index of blood indicated that there is no significant different among every group. The results of pathohistology checks indicated that the liver and the kidney was slightly inflamed in high group. The results showed that difloxacin hydrochloride suspension emulsions injection has no muragenic toxicity to KM mice. The results of teratogenicity suggested that difloxacin hydrochloride affected embryo development significantly at the dosage of 350 mg/kg by causing fetuses dead and skeletal malformation. The severity of the embryo/fetal toxicity has effective relation to the dose. In a conculsion, there is little acute toxicity, no accumulative toxicity of difloxacin hydrochloride suspension emulsions injection, but had some toxicity when administered with a high dosage for a long time. 2 Study on the residues of difloxacin hydrochloride in swine tissues We present a method based on reverse-phase high performance liquid chromatogram for determining residues of difloxacin hydrochloride in swine tissues. The HPLC system consisted of C18 column (250 mm×4.6 mm,5 μm) and the mobile phase was 2.028 g Sodium Dihydrogen Phosphate in 1 000 mL water- acetic acid 10 mL:Acetonitrile (70∶30),and the detection wavelength was 280 nm. Three concentration levels(20,100,500 μg/kg) of difloxacin hydrochloride in the blank tissues were analysed, the recovery of all samples were exceed 75 %, and the average recovery rates in muscle,liver,kidney,lung and skin+fat was84.72%、80.17%、76.78%、77.90%、79.61% respectively, the intra-day coefficient of variance was between1.09 % and 5.96 %, the inter-day coefficient of variance was between 1.17% and 4.97%. The limit of detection (LOD) of difloxacin hydrochloride in tissues was 10μg/kg. The linear ranges of difloxacin hydrochloride sulphate was 10~1 000 μg/kg. Difloxacin hydrochloride was administered intramuscularly to swines at a dosage of 5 mg/kg ，32-day of withdrawal time was recommended.