Preparation And Preliminary Evaluation Of The Tilmicosin Phosphate Thermosensitive In Situ Gel For Injection

Tilmicosin is a semi-synthetic macrolide antibiotic,specifically used by livestock and poultry.Its structure and antibacterial effect are in the same ring as erythromycin and tylosi n.All Gram-positive bacteria,some gram-negative bacteria,mycoplasma,and spirochetes are sensitive to it.It is mainly used for the treatment of infectious diseases caused by susceptible bacterial infections in animals such as livestock,cattle,sheep,chickens and pigs.Tilmicosin is insoluble in water,and its phosphate phosphate tilmicosin is mainly used clinically.The mechanism of action and antibacterial effect of tilmicosin phosphate are similar to that of tilmicosin.Thermosensitive in-situ gel injection refers to a polymer material that is injected and a dministered in a solution state,which can respond to temperature stimuli at the drug site,re versibly transforms in a dispersed state or conformation,and forms a semi-solid drug reser voir.Temperature-sensitive in-situ gel injection has become a new type of drug delivery sy stem and has received a lot of research in the field of pharmaceutics and biotechnology.In this study,a thermosensitive in-situ gel injection of tilmicosin phosphate was prepared by cold-dissolving method.The results showed that P407 and P188 had a significant effect on the gelation temperature,and sodium sulfite and edetate had no significant effect on the gelation temperature;tilmicosin phosphate increased the gelation temperature of the in-situ gel;the ratio was The gelling temperature of 23%P407+6%P188+0.2%sodium sulfite+0.01%disodium edetate+10%tilmicosin(based on tilmicosin)was 36.8°C.In order to investigate the characteristics of temperature-sensitive in situ gel of tilmicosin phosphate,an analytical method for the determination of tilmicosin by UV spectrophotometry was established.The results showed that the linear relationship between the absorbance and concentration of tilmicosin was good when the concentration of tilmicosin was 12-28?g/mL.The standard curve equation was:A=0.0209C-0.0071,R~2=0.9998.This method has high precision.Reproducibility and recovery are good.The in vitro and in vivo gelling properties and in vitro release properties were examined.The results showed that the gelation effect was obvious in vivo and in vitro.The gelation phenomenon could be rapidly occurred within 1 min at 37.5°C and injected into the body.The in vitro release time was prolonged to about 2 times.At 2 h,the tilmicosin phosphate solution was obtained.The cumulative release rate was 55.3%and the gel was only 31.2%.At 5 h,the cumulative release rate of the solution was 91.1%and the gel was only 53.4%.The rabbits were examined for muscle irritation and the acute toxicity of tilmicosin phosphate thermosensitive in situ gel injection was studied using a modified fistula method.The results showed that the temperature sensitive in situ gel injection of tilmicosin phosphate stimulated muscles from grade 1 to grade 2 with less stimulation and could be used for intramuscular injection;mice were injected intraperitoneally with LD50=302.691mg/kg,95%The letter limit is 269.421 mg/kg to 340.095 mg/kg,and the acute toxicity is small.The temperature-sensitive in-situ gel injection of tilmicosin phosphate prepared in this experiment was prolonged in vitro compared with the aqueous solution of tilmicosin phosphate,and its acute toxicity was small.Therefore,it has good development prospect and clinical application value.