The MRLs Standards Established For Robenidine Hydrochloride In Rabbits Edible Tissues

Robenidine hydrochloride, is {1,3-bis [( p-chlorobenzylidene) amino] guanidine hydrochloride}, is a synthetic anti-coccidiosis medicine. This medicine was on the market at early 70 s of the last century in the United States and was widely used as feed additives,mainly used for the intervene and treatment of acute coccidian of chickens, it is effective with Eimeria coccidium, such as Eimeria tenella, Eimeria Brandt and Eimeria. Currently robenidine is mainly used for prevention and treatment of chickens, rabbits and aquatic animals’ parasitic infections in China. This thesis include three parts: The pharmacokinetics and bioavailability of robenidine hydrochloride in rabbit plasma; Robenidine hydrochloride in rabbit tissues distribution and elimination; The MRLs standards established for robenidine hydrochloride in rabbits edible tissues.A total of twelve healthy rabbits were allotted to two groups and received single intravenous administration at the dose of 2 mg·kg-1 and single oral administration at the dose of 100 mg·kg-1 respectively, then collected the blood samples. 1% ethyl acetate was used to abstract robenidine from blood samples, and redissolved by methanol after dry up.Filter the samples by 0.22μm filter membrane for high-performance liquid chromatography(HPLC) analysis. limit of detection was 0.01μg·m L-1, limit of quantitation was 0.02μg·m L-1,recovery was 71.22~109.75%. After i.v. injection, AUC was 1.72 μg·h·m L-1, plasma clearance(CI) was 1.17 L·h-1·kg-1, the volume of distribution was 2.87 L·kg-1, Vd(ss)为 1.55L·kg-1 and the elimination t1/2 was 1.72 h. The volume of distribution following i.v.administration was large, it shows that the drug is widely distributed in rabbits and eliminated quickly. It’s could be eliminated in 6 hours as the dose of 2.00 mg·kg-1 After oral administration at the dose of 100.00 mg·kg-1, the absorb of the robenidine was very slow, tmax was 20 h, Cmax was 0.32 μg·m L-1, AUC0-t was 6.33 μg·h·m L-1, indicates that the amount of drugs into the body is very low. The CI was 16.68 L·h-1·kg-1, elimination t1/2 was8.94 h. it shows that the drug is widely distributed in rabbits and eliminated slowly.Statistical analysis on plasma showed that the bioavailability following oral administrationwas 7.36%, indicates that after oral administration of robenidine hydrochloride, the drug was rarely absorbed into the blood, was excreted as prototype.25 rabbits administration robenidine 15 mg·kg-1 for seven days, and five animals were randomly killed every time point, collect muscle, liver and kidney. Samples are extracted by chloroform-methanol mixture, using HLB purification, was measured by HPLC. The method in various tissues Robenidine LDQ were 0.01 mg·kg-1, the LOQ was 0.02 mg·kg-1.In 0.05, 0.2,2 mg·kg-1 groups, muscle recovery are 81.91%~109.75%, and the recovery of kidney is 83.56%~104.46%, recovery of the liver is 84.06%~103.66%. The results of experiment illustrated that robenidine hydrochloride have significantly different metabolic rate in different tissues, and rapid eliminate in muscle and kidney tissue, but not in liver tissue. Robenidine is not only the highest residue concentrations in liver, but also is the slowest elimination of residue. In rabbits, the target tissue is liver.According to the relevant literature of toxicology and metabolism studies, we consider the NOAEL of Robenidine in rabbit is 11 mg·kg-1·bw·d-1. The safety factor is 100.Acceptable Daily Intake is 0.11 mg·kg-1·bw·d-1. Robenidine hydrochloride Consider with robenidine hydrochloride in rabbits bioavailability and tissue residue depletion data, the safety and quality of animal products were analyzed. The MRLs of robenidine hydrochloride in rabbits as: liver 250μg·kg-1, kidney was 100μg·kg-1. Combined with China’s actual situation of aquaculture, estimation the withdrawal period is 5 days.