Preparation Of Tilmicosin-γ-Cyclodextrin Inclusion Complex And The Pharmacokinetics In Pigs

In this research,γ-cyclodextrin as the The carrier was used to prepare tilmicosin inclusion complex by aqueous solution stirring method.Using product yield and inclusion rate as evaluation indexes,the influence of materials rate,stirring time,stirring temperature and stirring speed on the yield and inclusion rate of inclusion complex were discussed.The best inclusion conditions were selected by statistical methods.Different methods were used to validate inclusion complexes.The stability and pharmacokinetics of the tilmicosin inclusion complex in healthy pigs were investigated to provide a method basis for the research of the new preparation for veterinary use of tilmicosin.The optimal preparation method of inclusion complex was obtained by orthogonal experiment design as follows:the molar ratio of tilmicosin toγ-cyclodextrin was 1:4,the temperature of inclusion was 50℃,the inclusion time was 30 h,and the stirring speed was 400 r/min.X-ray diffraction method showed that the characteristic peak ofγ-cyclodextrin disappeared,which was different from the chromatogram of tilmicosin andγ-cyclodextrin,indicating thatγ-cyclodextrin inclusion tilmicosin formed a new phase.In the IR spectra,the characteristic peaks of tilmicosin in the inclusion complex spectrum changed in shape,position and intensity,and it is obvious that tilmicosin andγ-cyclodextrin interact to form the tilmicosin inclusion complex.In the DSC spectra,the inclusion complex had an obvious thermal effect at 34.9℃～69.3℃,and reached the maximum at 86.4℃.The characteristic endothermic peak ofγ-cyclodextrin disappeared,which proved that tilmicosin andγ-cyclodextrin interacted and had inclusion behavior,forming a new phase.In the SEM spectra,the results showed that the inclusion complex of tilmicosin was irregular and fragmented,which was different from that of the single sample and the physical mixture of the two.It was proved that the inclusion complex of tilmicosin is a new phase.From the phase solubility curve,it can be seen thatγ-cyclodextrin has obvious solubilization effect on tilmicosin.The solubility of the inclusion complex was 31 times higher than that of the original compound,and it was soluble in water.The results of stability tests showed that the inclusion complex had good tolerance to high temperature,strong light and high humidity.High performance liquid chromatography method was chosen during the research.The mobile phase was prepared by acetonitrile,water,tetrahydrofuran and dibutylamine phosphate in a certain proportion.Under certain detection conditions,the standard working curve has a good linear relationship.The recoveries of plasma tilmicosin were 83.23±5.59%～108.29±2.19%,the intra-day coefficient of variation was 2.02%～8.45%,and the inter-day coefficient of variation was 1.39%～6.20%.The specificity of the method showed that the peak time of the sample was fast,the peak shape was clear,and the strength was not disturbed by the heteropeak.The process of plasma sample processing was simple.This method was simple,reliable and accurate,and could be used for the pharmacokinetics research of tilmicosin in pigs.In this research,10 healthy piglets were selected,the weight of piglets was evenly,and the piglets were randomly divided into two groups,each piglet to 30㎎/㎏single dose by mouth filling and suit for tilmicosin and its inclusion complex.Samples were taken at set time intervals.The results showed that the concentration-time relationship of tilmicosin and inclusion complex in blood in healthy pigs was consistent with the first-order absorption two-compartment model.The pharmacokinetic parameters of tilmicosin and inclusion complex in healthy pigs were:T_maxwere 2.4 h and 2.4 h;C_maxwere 1.58μg/m L and 2.46μg/m L;AUC were36.28μg·h/m L and 42.62μg·h/m L;T_1/2βwere 50.22 h and 53.11 h;CL were 0.81L/kg/h and 0.52 L/kg/h;Pharmacokinetic parameters of tilmicosin and inclusion complex were compared.The peak concentration(C_max),peak time(T_max),elimination half-life(T_1/2β),area under curve（AUC）and clearance rate（CL）of the inclusion complex group were 1.56,1,1.06,1.17 and 0.64 times higher than those of the tilmicosin group,respectively.Tilmicosin and inclusion complex were eliminated slowly in healthy pigs.Compared with the two,inclusion complex had higher relative bioavailability.