Residues of endosulfan in the tissues of lactating goats

SUMMARY: The sites of tissue accumulation in lactating goats of the organochlorine insecticide endosulfan were studied. Twelve lactating goats were dosed orally with endosulfan (1 mg/kg body weight per day) for 28 days. Groups of 3 animals were killed on days 1, 8, 15, and 21 after endosulfan treatment ended and their tissues examined for the presence of endosulfan. Total residues of α and β endosulfan and endosulfan sulphate (mg/kg) were detected in kidney (0.29), gastro-intestinal tract (0.20), liver (0.12), brain (0.06), muscle and spleen (0.04), lung and heart (0.01) and milk (0.02) on the flrst sampllng day but within 15 days, concentrations had fallen to < 0.01 mg/kg in all tissues except kidney (0.20). Endosulfan could not be detected in animals 21 days after dosing had ceased. The residue in milk could only be detected on day 1 of sampling. This study indicates that kidney rather than fatty tissue should be used to monitor the presence of endosulfan in animals intended for human consumption.     

液相色谱-串联质谱法研究地克珠利在家兔组织中残留及消除规律

[目的]建立一种检测家兔组织中地克珠利含量的液相色谱-串联质谱法（LC—MS／MS）,研究地克珠利在家兔组织中的残留及消除规律。[方法]选择48只家兔（雌雄各半）,在饲料中加入10g／1000kg地克珠利混饲,连续饲喂30d。分别于休药后的第0、1、2、3、4、5、6天,每个时间点随机处死6只家兔（雌雄各半）,取肌肉、肝脏、肾脏组织,DMF,乙腈沉淀法提取并用LC—MS,MS法检测地克珠利残留量。[结果]地克珠利在肾脏中的残留量最高（休药0d为912．6μg／kg）,肝脏次之（休药0d为156．μg／kg）,肌肉最低（休药0d为43．1μg／kg）,在肾脏中的消除速度最快。[结论]该方法适于检测家免组织中的地克珠利含量。休药0d即可满足欧盟要求     

Determination of sulphachloropyrazine-diaveridine residues by high performance liquid chromatography in broiler edible tissues

Diaveridine (DVD) is used in combination with sulphachloropyrazine (SPZ) as an effective antibacterial agent and antiprotozoal agent, respectively, in humans and animals. To gain a better understanding of the metabolism of SPZ and DVD in the food-producing animals, a high performance liquid chromatography (HPLC) method to determine and quantify sulphachloropyrazine (SPZ) and diaveridine (DVD) suspension residues from broilers is reported. Thirty healthy chickens were orally administered with sulphachloropyrazine-diaveridine (SPZ-DVD) suspension in water of 300 mg/l (SPZ) per day for seven successive days. Six chickens per day were slaughtered at 0, 1, 3, 5 and 7 days after the last administration. This procedure permitted SPZ and DVD to be separated from muscle tissue, liver, kidneys and skin with fat after extraction with acetonitrile and acetone under slightly acidic conditions. From the detected residuals in different tissues, we found that SPZ was quickly eliminated in liver and muscle, and slowly eliminated in kidney and skin with fat. DVD was quickly eliminated in liver and slowly eliminated in kidney. The withdrawal period of SPZ was 3.26, 3.72, 4.39 and 5.43 days in muscle, liver, kidney and skin with fat, respectively. The withdrawal period of DVD was 4.77, 4.94, 6.74 and 4.58 days in muscle, liver, kidney and skin with fat, respectively. Therefore, the suggested withdrawal period for SPZ-DVD suspension should be 7 days after dosing for seven successive days.     

恩诺沙星可溶性粉在白羽乌骨鸡组织中残留消除规律研究

为研究恩诺沙星可溶性粉在乌骨鸡体内的残留消除规律。50只11日龄健康白羽乌骨鸡,随机分为2组,给药组40只,对照组10只,给药组混饮恩诺沙星水溶液,浓度为75 mg/L,2次/d,连续用药5 d,对照组不给任何抗菌药物,与给药组同环境饲养。在最后一次给药后9、20、40、70、106 d采集肌肉、肝脏、肾脏、皮脂等样本,经LC-MS/MS法测定组织中的恩诺沙星及环丙沙星残留量,并利用WT1.4软件计算休药期。恩诺沙星可溶性粉在乌骨鸡肌肉、肝脏、肾脏及皮脂中的休药期分别是102.48、0、41.93、116.38 d。为保证消费者健康和食品安全,推荐恩诺沙星可溶性粉在乌骨鸡体内的休药期应大于117 d。     

Ceftiofur distribution in plasma and tissues following subcutaneously administration in ducks

A study was performed to determine the residues in blood and edible tissues of healthy ducks (25 days old, mean body weight 1.0+/-0.13 kg) after subcutaneous administration of ceftiofur sodium at a dose rate of 2 mg/kg body weight (Group I) and 4 mg/kg body weight (Group II). Blood, muscle, liver, kidney, and fat samples were collected from all of ducks on the 1st, 2nd, 3rd, 4th, and 5th day after treatment of drug, and ceftiofur was analyzed with a high-performance liquid chromatography (HPLC) assay with results reported as ceftiofur-free acid equivalent (CFAE). To study the spiked recovery, blank plasma and tissues were spiked with two different concentrations of ceftiofur sodium (0.1, 0.5 microg/g). Average recovery values for all samples ranged from 70.3 to 87.3%. In the group I, desfuroylceftiofur acetamide (DCA) was not detected in all of plasma, muscle, liver, and fat tissues on the 1st day after treatment. But, kidney samples on the 1st day were detected DCA (0.059+/-0.01 microg CFAE/g tissue). On the 2nd day of post-treatment, the concentrations of DCA in all tissues were lower than the detection limit, 0.05 microg CFAE /g tissue. In the group II on the 1st day after treatment, the concentration of DCA was 0.124+/-0.06 microg CFAE/g tissue, 0.103+/-0.03 microg CFAE/g tissue, and 0.071+/-0.010 microg CFAE/g tissue in plasma, kidney, and muscle samples, respectively. On the 2nd day after treatment of ceftiofur, the concentrations of DCA in all tissues were lower than 0.05 microg CFAE/g tissue. According to our results, the concentrations of DCA on the 1st day after treatment with 2 mg/kg body weight were below 0.05 microg CFAE/g tissue equivalent in all tissues except for kidney. On the 2nd day after administration at the dose of 4 mg/kg body weight, no DCA was also detected in all of the tissues although DCA was detected in all samples on the 1st day.     

Residues of spinosad in the tissues of sheep after aerosol treatment of blowfly myiasis

OBJECTIVE: To measure the residues of spinosad and chlorhexidine in the tissues of sheep after treatment of blowfly strike. PROCEDURE: Fourteen sheep with natural myiasis and 12 with artificial infestations of Lucilia cuprina larvae had the wool removed over their infestations and were treated with an aerosol wound dressing containing spinosad and chlorhexidine. Sheep were killed up to 14 days after treatment and residues of the chemicals measured in tissues. RESULTS: Chlorhexidine was not detected in any tissue. Residues of spinosad were highest in fat, lowest in muscle and intermediate in liver and kidney. The highest residue detected was 0.2 mg/kg spinosad in perirenal fat 7 days after generous treatment of a sheep with a large fly strike. Residues of spinosad in fat peaked 3 to 7 days after treatment and 1 to 3 days after treatment in liver and kidney. CONCLUSION: These studies present a realistic worst-case in struck sheep and at the highest dose studied, equivalent to 5.8 mg spinosad per kg body weight, the maximum residue detected of 0.2 mg/kg in peri-renal fat was 20% of the Australian maximum residue limit. Muscle, liver and kidney residues of spinosad were also below the Australian maximum residue limits at all times.     

Serum pharmacokinetics of oxytetracycline in sheep and calves and tissue residues in sheep following a single intramuscular injection of a long-acting preparation

The pharmacokinetics of a long‐acting oxytetracycline (OTC) formulation (Liquamycin® LA‐200®) injected intramuscularly (i.m.) at a dose of 20 mg/kg were determined in four calves and 24 sheep to determine if the approved label dose for cattle provided a similar serum time/concentration profile in sheep. The AUC for the calves was 168±14.6 (μg ? h/mL) and was significantly less than the AUC for sheep (209±43 μg ? h/mL). Using the standard two‐stage approach and a one‐compartment model, the mean Cmax for the calves was 5.2±0.8 μg/mL, and for the sheep was 6.1±1.3 μg/mL. The mean terminal phase rate constants were 0.031 and 0.033 h, and the Vdss were 3.3 and 3.08 L/kg for the calves and sheep respectively. Analysis of the data using the standard two‐stage approach, the naive pooled‐data approach and a population model gave very similar results for both the cattle and sheep data. Sheep tissue residues of OTC in serum, liver, kidney, fat, muscle and injection site were measured at 1, 2, 3, 5, 7 and 14 days after a single i.m. injection of 20 mg/kg OTC. Half‐lives of OTC residues in the tissues were 38.6, 33.4, 28.6, 25.4, 21.3, and 19.9 h for injection site, kidney, muscle, liver, mesenteric fat and renal fat, respectively. The ratio of tissue to serum concentration was fairly consistent at all slaughter times, except for the fat and injection sites. The mean ratios were 1.72, 4.19, 0.11, 0.061, 0.84 and 827 for the liver, kidney, renal fat, mesenteric fat, muscle and injection sites, respectively. The tissue concentrations of OTC residues were below the established cattle tolerances for OTC in liver (6 p.p.m.), muscle (2 p.p.m.) and kidney (12 p.p.m.) by 48 h, and in injection site muscle by 14 days after the single i.m. injection of 20 mg/kg.     

Tissue residues of some sulphonamides in normal and Eimeria stiedai infected rabbits.

Tissue residues of sulphadiazine (SDZ), sulphadimidine (SDD) and sulphquinoxaline (SQ) were studied in healthy and E. stiedai infected rabbits following oral administration of 0.5 g/l drinking water for 5 days. The solid-phase extraction and HPLC was used to determine the concentration of the three sulphonamides in a single tissue sample. SDZ was detected in the liver and kidney in concentrations below the tolerance levels at day 5 and no residues could be detected at day 7 after drug withdrawal. SDD and SQ were detected in all of the tested organs of healthy rabbits up to day 5, where the highest concentration was reported in the liver (0.08 +/- 0.02 and 0.09 +/- 0.02 g/g respectively). In infected rabbits, the three sulphonamides were detected up to day 7 in concentrations higher than the tolerance limits (> 0.1 g/g) in the liver and kidney and lower levels in other tissues. A withdrawal period of 4 days for SDZ and 5 days for SDD and SQ in healthy rabbits and 7 days for SDZ and 8 days for SDD and SQ in E. stiedai infected rabbits is suggested.     

猪肾脏等组织中盐酸莱克多巴胺的HPLC检测方法及其残留消除

本研究建立了猪肝脏、肾脏、肌肉和脂肪中盐酸莱克多巴胺的高效液相色谱检测方法。方法的检测限为1ng/g,定量限为2 ng/g,肝脏的平均回收率在73.4%～83.2%,变异系数在2.1%～6.6%;肾脏的平均回收率在73.1%～95.5%,变异系数在3.8%～4.0%;肌肉的平均回收率在80.7%～82.5%,变异系数在4.9%～9.1%;脂肪的平均回收率在73.3%～78.8%,变异系数在2.9%～6.7%。对60头健康猪以18 mg/kg的剂量混饲给药28d,停药饲喂14 d。在给药7、142、8 d和停药1、2、3、7、9、14 d分别屠宰6头猪,取各组织进行残留量测定。结果显示：肾脏中残留量最高,肝脏其次,残留量在停药期间较给药期间显著降低。其中肾脏和肝脏中的残留量分别在停药14 d、停药9 d后降至定量限以下;肌肉和脂肪中的残留量显著低于肾脏和肝脏,给药28 d时,残留基本低于定量限;停药1 d时均低至检测限以下。     

Disposition kinetics of doxycycline in chickens naturally infected with Mycoplasma gallisepticum

1. The pharmacokinetic properties of doxycycline were determined in healthy chickens and chickens naturally infected with Mycoplasma gallisepticum after a single intravenous (i.v.) and oral administration of the drug at 20 mg/kg body weight. Tissue residues of the tested drug after an oral dose of 20 mg/kg given twice daily for 5 consecutive days were also estimated in diseased chickens. 2. The plasma concentrations of doxycycline following single i.v. and oral administration were higher in healthy chickens than in diseased ones. Following i.v. injection, the elimination half-life (t1/2beta), distribution half-life and mean residence time (MRT) were longer in healthy chickens than in diseased birds. The values of total body clearance (ClB) and volume of distribution (Vdss) were larger in healthy chickens than in diseased birds. 3. After single oral administration, the absorption half-life (tl/2ab) and the elimination half-life were longer in normal birds than in diseased ones. The maximum plasma concentration of the drug was higher in normal chickens than in diseased ones. 4. Following repeated oral administration, the concentration of doxycycline in all tissues except muscle was higher than the corresponding concentrations in plasma. Concentrations of doxycycline in different tissues were in the following order: kidney > liver > lung > muscle. The drug was detected in liver and kidney in substantial concentrations on d 5 post administration of the last dose whereas, on d 7, its concentration in all tissues was below the lower limit of the sensitivity of the assay method used. Because of the low sensitivity of the microbiological assay method used in this study, a safe withdrawal time for doxycycline in diseased birds could not be estimated for the meanwhile.     

甲苯咪唑在鳗鲡体内的药物代谢及组织残留

采用反相高效液相色谱法定量检测抗鳗鲡拟指环虫药物甲苯咪唑及其代谢产物羟基甲苯咪唑和氨基甲苯咪唑。研究欧鳗经1mg／L甲苯咪唑药浴处理后,其皮肤、脂肪、肌肉、肝脏和肾脏中甲苯咪唑的代谢和残留情况。实验结果表明：药浴时,欧鳗在24h内快速吸收药物,皮肤上和脂肪中含有高浓度甲苯咪唑,且甲苯咪唑在欧鳗肝脏和肾脏中转化成羟基甲苯咪唑和氨基甲苯咪唑,其中氨基甲苯咪唑是主要代谢产物;三种化合物在皮肤上的残留量明显高于肌肉;鳗鱼可食用部位（肌肉和皮肤）中甲苯咪唑和羟基甲苯咪唑在3d内代谢浓度降至药残最高限量（0．1mg／kg）,5d内可完全降解消除．但氧墓甲苯眯唑在停药12d后的含量仍高于0．1mg／kg。     

Determination of residues of pyrethroid and organophosphorous ectoparasiticides in foods of animal origin

Analytical methods were introduced for the determination of residues of ectoparasiticides containing pyrethroid and organophosphate active ingredients in foods. Milk and edible tissues of cows treated with three experimental ectoparasiticides (containing cypermethrin + diazinon, deltamethrin + diazinon and alphamethrin + diazinon, respectively) were assayed for the presence of active ingredient residues. Synthetic pyrethroid residues were not detected in any of the samples processed. Diazinon residues could only be detected in milk samples taken on the first day after treatment (0.005-0.025 mg/kg) and in liver and fat tissue samples taken on the day of slaughtering (0.12 and 0.01 mg/kg, respectively). Permethrin and propetamphos residues were determined in the skin, meat and liver of chickens kept on 'Blotic-B' treated litter and in eggs collected at different times after the treatment of layer houses. Permethrin residues could not be detected in any of the samples (< 0.01 mg/kg). Meat and fat tissues of chickens slaughtered on the day after treatment contained small amounts of propetamphos (0.003 and 0.02 mg/kg, respectively). In the case of chickens kept on the treated litter and slaughtered after one week, active ingredient was not detected in meat, but 0.006 mg/kg propetamphos was present in the fat. The residue content of other samples (liver, egg) was below the detection limit of the applied method at all sampling times. From the food toxicological point of view these pesticide combinations can be used safely if the recommended withdrawal period is observed between ectoparasiticide administration and slaughter.     

猪肉和牛奶中10种磺胺类药物残留检测超高效液相色谱法研究

建立了猪肉和牛奶中磺胺嘧啶（SD）、磺胺噻唑（ST）、磺胺二甲嘧啶（SM2）、磺胺甲氧嗪（SMP）、磺胺氯哒嗪（SPD）、磺胺间甲氧嘧啶（SMM）、磺胺甲基异嗯唑（SM2）、磺胺氯吡嗪（Esb3）、磺胺地索辛（SDM）和磺胺喹嗯啉（SQ）共10种磺胺类药物残留检测的超高效液相色谱（UPLC）法。色谱条件：色谱柱为Acquity UPLC BEH C18柱（2．1mm×50mm,1．7μm）;流动相为50％甲醇乙腈溶液-2％乙酸水溶液,梯度洗脱;紫外检测波长270nm;柱温30℃;进样量4μL;外标法定量。结果表明：10种组分在20～1000ng／mL浓度范围内,呈良好线性关系,相关系数R^2均大于0．998;方法检出限为20ng／g,定量限为50ng／g;在猪肉和牛奶中添加浓度分别为50、100、200ng／g时,平均回收率为75．1％～99．8％,批内、批间平均RSD均小于13．2％。     

Antibiotic and sulfonamide agents in bob veal calf muscle, liver, and kidney

During the fiscal year 1988, USDA-FSIS detected 3,095 antimicrobial violations in bob veal calves, using the calf antibiotic and sulfonamide test. Of the 3,095 carcass submissions involved, 945 were tested further to identify the causative agents. The results of tests on the available kidney, liver, and muscle specimens are reported. Kidney specimens yielded a specific agent most often (71.2%), with neomycin (42.6%) being cited most among agents found in kidneys. Neomycin was found less frequently in liver (4.5%) and muscle (0.2%). Among all tissues, unidentified microbial inhibitors were either the largest or second largest category found (kidney, 10.5%; liver, 27.1%; muscle, 7.8%), and no other agent exceeded 7.0% (streptomycin in kidney). The proportion of liver and muscle specimens that had unidentified microbial inhibitors is particularly important because the next most common classes were streptomycin in liver at 5.5% and sulfamethazine in muscle at 2%. The frequency of unidentified microbial inhibitors may justify the addition of tests to the FSIS battery for identification of agents. Not all tissues were tested for sulfonamides, hence these agents are likely to have been underreported. Less than 10% of the muscle specimens evaluated yielded an agent, suggesting most calf antibiotic and sulfonamide test-positive carcasses may have been safe with regard to residues in meat, although organs might have been adulterated. Specimens for verification were not selected completely randomly from the population of all calf antibiotic and sulfonamide test-positive animals and calves selected for testing were not chosen strictly by random sampling; therefore, extrapolation of the contents of this report to the bob veal calf industry must be done with caution.     

Pharmacokinetics of amoxycillin and the rate of depletion of its residues in pigs

Six pigs were used in a two-period crossover study to investigate the pharmacokinetics of amoxycillin after single intravenous and oral doses of 20 mg/kg bodyweight. Twelve pigs were used to study the residues of the drug in muscle, kidney, liver and fat after they had received daily oral doses of 20 mg/kg amoxycillin for five days. The mean (sd) elimination half life (t1/2beta) and mean residence time of amoxycillin in plasma were 3.38 (0.30) and 3.54 (0.43) hours, respectively, after intravenous administration and 4.13 (0.50) and 4.47 (0.30) hours, respectively, after oral administration. After oral administration, the maximum plasma concentration (Cmax) was 7.37 (0.42) microg/ml and it was reached after 0.97 (0.29) hours. Six days after the last oral dose, the mean concentration of amoxycillin in the pigs' kidneys was 21.38 ng/g and in the liver it was 12.32 ng/g, but no amoxycillin could be detected in fat or muscle; the concentrations of amoxycillin in edible tissues were less than the European Union maximal residue limit of 50 microg/kg.     

A radioimmunoassay method for the measurement of residues of the anabolic agent, hexoestrol, in tissues of cattle and sheep

A radioimmunoassay (RIA) method for hexoestrol using an antiserum against hexoestrol-carboxypropyl ether-BSA and H³-hexoestrol was used to measure the concentrations of residues of hexoestrol in 0.1 ml biological fluids and 1 g edible tissues of implanted cattle and sheep. A preliminary ether extraction of biological fluids was necessary before RIA. The ether extract from tissues was further purified by solvent partition and silica gel column chromatography before RIA. Conjugates of hexoestrol were measured after enzymatic hydrolysis to free hexoestrol. In untreated animals residues were either not detected or very low in all tissues except urine from sheep. The method has a lower limit of detection of approximately 0–10 pg/ml for biological fluids in cattle and 20–100 pg/g for tissues in both sheep and cattle but the lower limit of detection in sheep urine was 70–294 pg/ml urine. In two heifers implanted with 60 mg hexoestrol and slaughtered 2 and 7 days after implantation, residues of hexoestrol were detected in all tissues except muscle with highest concentrations between 2 - 17 ng/g in urine, bile and kidney. The concentration of residues in steers which had been implanted with 45 mg or 60 mg hexoestrol and slaughtered at 90 days after implantation were 0, < 50, 46–96 and 200 pg/ml or g of plasma, muscle, liver and urine, respectively. The concentrations of hexoestrol in sheep implanted with 15 ml hexoestrol and slaughtered after 60 days were 70, 0, 964, 3100 and 4074 pg/g or ml of muscle, fat, liver, kidney and urine, respectively. No hexoestrol was found in control untreated cattle and sheep. It was concluded that some residues of hexoestrol were present in the excretory fluids and tissues of cattle and sheep which had been implanted with hexoestrol at the recommended dose and slaughtered after the recommended withdrawal periods. However, the concentrations of hexoestrol in muscle and fat were extremely low or not detectable. The method could be used for the routine screening of animals for treatment with hexoestrol.     

Sulfonamide residues in eggs.

In two series of experiments lasting 3 days each, laying hens were medicated with sulfonamides via the drinking water. In the first experiment 8 laying hens were given sulfaquinoxaline (SQ) at a dose rate of 400 mg/l, while in the second trial 16 laying hens received a 3:5:5 sulfonamide mixture containing sulfaquinoxaline (SQ), sulfadimidine (SDI) and sulfamerazine (SMN), at a dose of 390 mg/l. According to the water consumption data, the hens' daily sulfonamide intake was 53.6 and 56.9 mg/kg body mass, respectively. Eggs laid during and in the first 10 days after the treatment were collected and assayed for sulfonamide residues by spectrophotometry. The detection limit of the method was 0.16 mg/l and the recovery percentage was between 70 and 80%. Sulfonamide was found to appear already in eggs laid after the first day of treatment. The absorption half-life of the drug was 0.4-0.6 day in the egg-white and 0.93-1.08 day in the egg-yolk. Peak drug level in the egg-white was measured on the last day of medication, while in the egg-yolk within 3 days after the end of treatment. The residue measured in the yolk was 13-16% of that found in the egg-white. Acetylated sulfonamide could be measured in the yolk for 3 days after the treatment: its level reached 15%. On the basis of the elimination rate, complete elimination of sulfonamides requires at least 5.2-7.4 days. Therefore, observance of the generally accepted withdrawal time of 10 days is indispensable.     

Radioimmunoassay of the anabolic agent zeranol. IV. The determination of zeranol concentrations in the edible tissues of cattle implanted with zeranol (Ralgro)

Rapid solvent extraction combined with a radioimmunoassay using a monoclonal antibody raised against a derivative of zeranol has been used to measure the residues of the anabolic agent zeranol in the edible tissues (muscle, liver, kidney and fat) of cattle treated with Ralgro. Calibration curves, both with and without, tissue extracts exhibit good parallelism. Regression analysis for the extraction of zeranol from tissues dosed with standard amounts of zeranol have correlation coefficients of 0.979, 0.991, 0.986 and 0.985 for muscle, liver, kidney and fat, respectively. The limits of decision defined as the mean value + 3 SD for the concentrations apparently observed (noise) in tissues from animals not treated with Ralgro were 278, 121, 373 and 110 ng/kg for muscle, fat, liver and kidney, respectively. In the tissues of 4 cows implanted with Ralgro (36 mg), and sampled 70 days after implanting, the highest concentration of zeranol in each tissue was 232 ng/kg (muscle), 391 ng/kg (liver), 287 ng/kg (kidney) and 293 ng/kg (fat), and residues were detected in all samples of fat (4), 3 kidney samples and 1 liver sample.     

氟苯尼考注射液在鸡体内残留消除研究

［摘 要］为研究氟苯尼考注射液在鸡体内的残留消除规律。本实验采用35只约3kg左右的健康白羽鸡,随机分为2组,给药组30只,对照组5只。给药组用药量为20mg/kg/次,每隔48小时用药1次,连用2次,对照组不给任何抗菌药物,与给药组同环境饲养。在最后一次给药6h、24h(1天)、72h(3天)、120h(5天)、168h(7天)时采集肉、肝、肾、皮脂样本,经LC-MS/MS法测定组织中的氟苯尼考及其标示物氟苯尼考胺残留量,并利用WT1.4软件计算休药期。结果显示：氟苯尼考注射液在鸡肌肉、肝脏、肾脏及皮脂中的休药期分别是3.41d、2.06d、2.25d、1.47d。为保证兽药使用安全、消费者健康和食品安全,推荐氟苯尼考注射液在鸡体内的休药期为4d。     

Serum pharmacokinetics and tissue and milk residues of oxytetracycline in goats following a single intramuscular injection of a long-acting preparation and milk residues following a single subcutaneous injection

Separate groups of goats were used to determine drug depletion patterns in serum (n=10), tissue (n=20) and milk (n=8) following a single intramuscular (i.m.) dose of 20 mg/kg of a long-acting oxytetracycline (OTC) formulation (Liquamycin LA-200). Milk residues were also determined following a subcutaneous (s.c.) administration of the same product at the same dose. Serum samples were taken for 24 h post-treatment and tissues (fat, liver, kidney, muscle and injection site) collected at 4, 7, 14, 21 and 28 days following injection. Milk from lactating goats was collected every 12 h for 8 days following both the i.m. and s.c. treatments utilizing an intervening 5-week washout period. Residues in serum and tissue were measured using a microbial inhibition assay, while milk residues were measured using both a microbial inhibition assay and a validated HPLC method. The serum pharmacokinetic parameters of OTC in goats were determined, with a mean AUC=67.4 microg h/mL, mean terminal half-life=14.4 h, and apparent clearance=0.33 L/kg h. Tissue half-lives could not be determined with confidence because the collection times provided only two points at which residues could be measured for most tissues. Oxytetracycline residues in all goat tissue samples measured less then cattle tissue tolerance by 96 h postdosing. One-compartment model describing milk depletion data for i.m. and s.c. dosing had terminal slope half-lives of 20.1 and 36.1 h, respectively. By 96 h post-treatment none of the milk samples contained OTC residues in excess of the cattle milk tolerance (0.3 p.p.m.). For both milk and tissue, the upper-bound 99% confidence intervals for the samples taken from goats 96 h postdosing were lower than approved cow milk and tissue tolerances.