| Macrolides are widely used as antiparasitic against endoparasite and ectoparasite.Spinosad is characterized by high efficiency,low toxicity,high selectivity and easy degradation in natural environments.And it is commonly used in animal husbandry and pet industry.In that case,spinosad,a class of macrolide drugs,is with great potential for development.At present,the spinosad commercial preparations mainly include oral chewable tablets and topical preparation.To reduce the dose of administrationand improve the bioavailability,a series of studies on a injection of spinosad was conducted.A sustained-release injection of spinosad was developed through the self-microemulsification method.Simultaneously,High Performance Liquid Chromatography(HPLC)and Enzyme-linked Immunosorbent Assay(ELISA)for the determination of Spinosad was established.A method for the determination of spinosad in plasma by high-performance liquid chromatography with ultraviolet detection was developed.Acetonitrile was used as the extractant solvent of spinosad in plasma,the sample was concentrated and purified by a nitrogen blow at 40℃.The concentrated sepinosad sample was analyzed by the Shimadzu(?)liquid chromatograph.The test conditions were as follows:Column:Waters C18 Mobile phase(4.6 mm × 250 mm,5 m)Mobile phase:Phase A(acetonitrile:methanol=1:1),Phase B(ultra-pure water)= 98:2 Flow rate:1.0ml/min;detection wavelength:246nm;column temperature:40℃;injection volume:10 μlThe standard curve equation is:Y=7478.2X+2434.5,R2=0.9999.The results showed that spinosad has a good linear relationship in the range of 0.391-100 ng/ml.The pharmacokinetics of a novel spinosad microcmulsion injection in New Zealand rabbits was studied at a dose of 0.25 mg/kg body weight.Two different assays,enzyme-linked immunosorbent assay(ELISA)and high performancce liquid chromatography(HPLC)were used to analyze the drug concentration and the PKsolver software non-compartmental model was used to calculate the pharmacokinetic parameters.The results showed that the main parameters of pharmacokinetics under HPLC and ELISA were as follows:peak time Tmax(4.00 ± 0.00),(2.67=1=0.67)h,peak concentration Cmax(363.25±13.39),(282.19±24.59)ng/mL,respectively.The half-life t1/2 was(81.24± 10.80)and(70.61 ± 15.38)h,respectively.The area under the curve was AUC of(17.52± 1.24)and(17.39±2.38)μg· h/mL,respectively.To compare the two detection methods under the same injection method and the same dose,the trend of changes in plasma concentrations were similar in both assays,but the actual measurement value such as the peak concentration Cmax,the difference was significant(P<0.05),the remaining parameters were not significantly different(P>0.05).Experiments show that:subcutaneous injection of spinosad has fast absorption,slow elimination and a long half-life of the drug that can take into effect on the parasite in New Zealand rabbits for a long time.At the same time,the pharmacokinetics of 1%spinosad microemulsion injection in Hainan black goats was studied at a dose of 5 mg/kg body weight.The test results under the HPLC method were as follows:Tmax was(2.2511.03)h,Cmax was(1140.27±72.13)μg/ml;t1/2 was(117.15±6.40)h;AUC was(65.96±39.80)μg/mL.h.The results of the two pharmacokinetic tests all showed that the microemulsion had a shorter peak time than other spinosyn routine preparations,and the tissue distribution in animals was more extensive.And efficacy test was carried out to verify the effect of spinosad injection against Hainan Black Goat t lice.In this study,the effects of different doses of spinosad o/w microemulsion injection(10mg/kg,5mg/kg,2.5mg/kg,1.25mg/kg body weight)versus traditional ivermectin injection(0.2mg/kg body weight)and ivermectin microemulsion injection in the treatment of lice were compared.The experiment was conducted in two farms in differernt seasons.Naturally lice infested goats were selected in the experiment in each farm according to pre-treatment lice counts.In winter experiments,At day 10 post-treatment,the reduction rates of lice of the spinosad o/w microemulsion injection treatment at 10mg/kg,5mg/kg,2.5mg/kg,1.25mg/kg was 84.06%,83.52%,90.00%,89.02%,repectively.At day 30 post-treatment,the reduction rate reached 100%,99.06%,100%,99.74%,cure rates reached 8/8(100%),7/8(87.5%),8/8(100%),7/8(87.5%).In summer experiments,two possiblely minimum effective dose were selected to verify their effectiveness under different climatic conditions.After 10 days of treatment,the reduction rate of lice was 77.90%and 82.22%,respectively.After 40 days,the reduction rate of lice increased to 88.51%and 87.02%.Compared with the winter experiment,the cure rates sharply decreased to 3/11(27.3%)and 3/12(25%),the hot and humid summer weather in Hainan Island might be conducive to the different result.The spinosad treatment also reduced wool damage in infested goats and helped goats gain weight.For the safety observation,spinosad at 20 mg/kg bodyweigh subcutaneous injection did not show adverse effects.Results of this study demonstrated that the off-label,experimental injectable formulation of spinosad is convenient to use,highly effective and safe for the treatment of the goat lice,and it also showed that the spinosad formulation had stable efficacy over a long period of time(a single administration for one month). |
PDF Full Text Request