Research And Preparation Of Tropicamide Thermosensitive In Situ Eye Gel

ObjectiveThe aim of this study is to prepare and evaluate tropicamide thermosensitive in situ eyegel. Get the optimized formulation with central composite design-response surface methodand rheological method, and investigate its quality, gel erosion and drug release behavior,eye retention time and irritation.Method1. Optimize formulation with central composite design-response surface methodP407and P188were used for the thermosensitive material and single factor experimentwas used to get the important factors, then central composite design-response surfacemethod was applied to optimize the formulations. The equation fitting was carried out bySPSS13.0to establish the mathematical relation between gelation temperature andthermosensitive material concentration. Then Matlab2011b was used to get the3D responsesurface and two dimensional contours. By overlying two dimensional contours, theoptimized region was acquired. Then representative formulations were chosen and used tovalidate the prediction. According to Chinese Pharmacopeia, osmotic pressure regulator,bacteriostatic agent and adhesion resistant materials were added to study the influence onthe gelation temperature of the formulations, and adjust thermosensitive materialconcentration to get the appropriate gelation temperature which met the eye applicationrequirements.2. Rheological evaluation of TR thermosensitive gelA Kinexus Pro rheometer was used to carry out the rheological evaluation test indynamic shock mode. Stress scan and temperature scan were used to get the linearviscoelastic region and the precise gelation temperature. In addition, frequency scan andgelation time scan were carried out to investigate the viscosity change and different gelationtime separately. 3. Quality studyHPLC was applied to establish the quantitative determination method. According toChinese Pharmacopeia, the properties, quantitative determination, initial stability and sterileexamination of TR thermosensitive gel were studied to evaluate the formulation.4. Gel erosion and drug release behavior study of TR thermosensitive gelGel erosion and drug release were investigated by member free method according tothe quantitative determination method.5. Eye retention time and irritation test studyTR thermosensitive gel and TR drops were labeled with fluorescein sodium, bycrossover design to get the retention time. And irritation test of TR thermosensitive gel wascarried out to evaluate the formulation with self-control and Draize score method.Results1. Single factor experiments show that concentrations of P407and P188are importantfactors to the gelation temperature. The gelation temperature goes down when concentrationof P407increases, which is exactly the opposite of P188. The equation which was imitatedwith SPSS13.0is T1=74.270-2.578X+0.934Y (r=0.9187, P <0.01); T2=89.264-3.018X+1.191Y (r=0.8899, P <0.01). The optimized region is obtained by Matlab2011b and4representative formulations are chosen to validate the prediction ability of the equation. Theresult shows that deviation is less than5%, which means the prediction ability is credible.After adding with the osmotic pressure regulator, bacteriostatic agent and adhesion resistantmaterials according to Chinese Pharmacopeia, gelation temperature goes down. Adjust theconcentration with the changes in gelation temperature, then the appropriate formulationsare obtained, which are A:20%P407-4%P188, B:20%P407-5%P188-0.5%HPMC K4M,C:21%P407-8%P188-0.5%HPMC K4M, D:22%P407-10%P188, E:20%P407-5%P188-1%HPMC E50, F:21%P407-6%P188and G:21%P407-9%P188-1%HPMC E50.All the formulations contain0.25%TR,0.03%ethylparaben and0.9%sodium chloride.2. Stress scan indicates that the linear viscoelastic regions of before and aftersimulated tear fluid are5Pa~13Pa and1Pa-13Pa respectively, so10Pa and5Pa are chosen tobe the stress for the next steps. G’ and G” shows an S-shaped curve with the increasedtemperature. When temperature is lower than gelation temperature, the thermosensitive gelis in a fluid liquid state; and with the temperature increasing to the gelation temperature, it transfers to a semisolid gel state. Meanwhile, G’, G” and phase angle go down with thetemperature increasing, which means the gel intension becomes weak. And viscosity η’decreases when the frequency increases. Gelation time decreases with the thermosensitiveexpients’ content increasing.3. The results of HPLC showed that the retention time of TR is7min, and expientshave no effect on the drug. The linear relation between peak area (Y) and concentration (C)of TR is Y=16.163C+52.731(R2=0.9997), which means good linear relation between themat concentration of19.9~199μg/mL.24h stability test and precision test show that the RSDis0.35%(n=6) and0.19%(n=6) separately. Percent recovery of low, medium and highconcentration is99.01%,98.94%and100.21%, with RSD0.97%,0.14%and0.12%(n=6)respectively.And quality study shows the gel is in fluid liquid state at room temperature andchanges to semisolid state at body temperature, and pH of the formulation is between6~7.In addition, sterile examination result meets the eye administration’s requirements.4. The gel erosion is in proportion to drug release, which says that the drug releasebehavior is controlled by gel erosion.5. The fluorescein-labeled test shows the retention time in rabbit eye ofthermosensitive gel and drops are20min and5min separately. The former is longer than thelatter. And irritation test shows that TR thermosensitive gel meets the eye administration’srequirements.ConclusionCentral composite design-response surface method and rheological evaluation are usedto design the experiments and optimize formulations, by which the suitable preparation foreye use is obtained. Then HPLC is applied to establish the content determination method,meanwhile gel erosion and drug release are also investigated. In addition, quality study, theretention time test and irritation test are carried out, results of which all meet the eyeadministration’s requirements. Eventually, the safe, quality controlled and effectivepreparation is obtained and has a good prospect in clinical use.