Development And Pharmacokinetic Evaluation In Hens Of Thiamphenicol Nanoparticles

Thiamphenicol（TAP）has been widely used by veterinarians due to its advantages of rapid,complete absorption and wide distribution after administration.Thiamphenicol has an effect on both gram-negative and gram-positive bacteria and is often used to treat respiratory and intestinal infections in large animals,poultry and aquatic animals.Thiamphenicol is slightly soluble in water,with low-solubility and high-permeability,which limits its clinical application to a certain extent.Making it into nanoparticles is an effective way to increase solubility and promote oral absorption.In this study,Thiamphenicol nanoparticles（TAP-NP）were prepared by emulsified solvent volatilization combined with single-factor test,and the physicochemical properties of TAP-NP prepared under optimal conditions and the pharmacokinetic properties of it in chickens were investigated,aiming to prepare TAP-NP with nanoscale particle size,improving the water solubility and absorption effect of drugs,in order to provide a new idea for the widespread application of Thiamphenicol and improve its mucosal adsorption and bioavailability.1.Preparation of TAP-NPEmulsified solvent volatilization was combined with single-factor test to screen out the optimal formula and preparation process for the preparation of TAP-NP.Single-factor test was used to investigate seven influencing conditions.The optimal conditions for the preparation of TAP-NP were finally determined as follows:the volume ratio of the oil phase to the aqueous phase was 1:5,the concentration of PVP K30 was 1‰,the homogenization was carried out at 6000 r/min for 5 min,and the homogenization pressure was cycled 7 times at 700 bar,and mannitol was used as the lyophilization protectant.The average particle size of TAP-NP prepared under the above conditions was 225.5±30.5 nm,and the average PDI was 0.260±0.02.2.Physicochemical characterization of TAP-NPThe drug content,solubility,dissolution and stability of TAP-NP were tested,and the results were as follows:the average value of thiamphenicol content in TAP-NP was（75.52±2.87）%,its solubility in water was 9.69±0.78 mg/m L,which was about 2.2 times of TAP,the solubility and dissolution rate were improved.TAP-NP was not sensitive to light and high temperature,but easily absorbed moisture and deliquescence,it is recommended to seal and place in a ambient temperature and no light environment for preservation.The physicochemical characterization of TAP-NP prepared under the optimal conditions were characterized by SEM,FT-IR,XRD and DSC.It can be seen from the SEM diagram that the appearance of TAP is irregular flakes or blocks of different sizes,and the TAP-NP were in the shape of long homogeneous rods;The FTIR results showed that the FT-IR spectrum of TAP-NP was similar to that of TAP,only a few absorption peaks were broadened,and the chemical structure of TAP was not changed.From the FT-IR,XRD and DSC results,it was clear that the crystalline structure of TAP-NP was changed and might exist in the amorphous state.3.Pharmacokinetic evaluation of TAP-NPGastric administration of 20 healthy laying hens,we collected subwing venous blood at different time points after the administration,measured the concentration of TAP in hen plasma by high performance liquid chromatography（HPLC）external standard method,plotted the blood concentration-time curveof TAP-NP group and TAP groupby Graph Pad Prism 8.0 software,processed the experimental data with DAS 2.0 and SPSS 25.0 software.The results showed that the HPLC chromatography baseline of the method was stable and there were fewer stray peaks.The precision,recovery rate and repeatability are in line with the test requirements.The pharmacokinetic parameters showed that the drug peak time(T_max)of the TAP-NP group was（0.700±0.258）h,which was significantly smaller than that of the TAP group,and the area under the drug concentration-time curve(AUC_0-∞)and the maximum blood TAP concentration(C_max)were（35.400±4.279）μg/L·h and（8.939±0.608）mg/L,respectively,which were both obviously higher than those in the TAP group,and the relative bioavailability of the TAP-NP group was about 1.71 times than that of the TAP group,which also indicated that the preparation of TAP into nanoparticles could promote the absorption rate and degree of absorption of the drug.The results showed that the particle size of TAP-NP prepared by emulsified solvent volatilization method in the study was in the range of 122～396 nm,and the solubilization effect was obvious.The chemical structure of TAP-NP didn’t change,but the crystalline structure changed,may be amorphous form,and TAP-NP can significantly improve the absorption status of TAP and increase the bioavailability,which provides an experimental reference basis for the research of new dosage forms of TAP.