Puerarin Temperature Sensitive Bioadhesive Eye In Situ Gel

Due to the special anatomic structure and efficient protective mechanisms,many challenges are presented in the development of novel ophthalmic dosage forms.Eye drops are the conventional dosage forms that account for 90%of currently accessible ophthalmic formulations.Despite the accurate dose,the convenient administration and the excellent compliance by patients,there are also many problems presented simultaneously:rapid drug elimination following the tear fluid soon after administration,short precorneal residence time,and lower bioavailability.Moreover, if entering the circulatory system,some drugs may cause systemic adverse effect.Due to the existence of the corneal physiologic barrier,many drugs have bad transcomeal permeability,are hard to maintain relatively high concentration in the site of intraocular illness and bring much greater therapeutic effect.To solve these problems, in this project,we adopted puerarin,which is an anti glaucoma drug,as the model drug,utilized the penetration enhancer to increase its transcomeal permeability,and developed a poloxamer analogs/carbopol-based in situ gelling and bioadhesive ophthalmic delivery system for puerarin.This system can be administrated as eye drops,which can reserve the merit of the conventional eye drops.After dilution by the tear fluid in the conjunctival sac,it can still convert to gel due to the physiologic temperature.Thus,it won't eliminate following the tear fluid,furthermore,it possesses bioadhesive property,can promise a relatively long precomeal residence time,and maintains an effect drug concentration continually,which overcomes the deficiency of the conventional eye drops.Six aspects were performed in this project, which present as following.(1) Effect of hydroxypropyl beta cyclodextrin(HPCD) on aqueous solubility and corneal permeation of puerarinThe solubility of puerarin with HPCD was investigated by phase-solubility method. The permeability of puerarin across the rabbit cornea was measured in vitro.The results indicate the solubility of puerarin increases linearly as the concentration of puerarin;HPCD can enhance the transcorneal permeability,of puerarin obviously. However,the apparent permeation coefficient of puerarin decreased as the concentration of HPCD increased.(2) The optimization and design of the pharmaceutical formulationsA two-factor,five-level central composite design-response surface methodology (CCD-RSM)was employed to the optimization procedure of the thermosensitive in situ gel.Finally,21.0%(w/v) poloxamer 407(P407) and 5.0%(w/v) poloxarner188 (P188)(P407/P188) were chosen as the optimal poloxamer gel matrix.Then,the type and concentration of the bioadhesive adjuvant were screened.As a result,0.1%(w/v) and 0.2%(w/v) carbopol 1342(CP1342) were selected for further investigation.In addition,other supplemental agents were screened as well.(3) In vitro evaluation of the pharmaceutical preparationsThe assaying method was established for the preparations.Rheological behavior, mucoadhesive force and in vitro puerarin release were estimated in this section. Results demonstrated that the shear stress of the two combined polymer solutions (P407/P188/0.1%CP1342 and P407/P188/0.2%CP1342) were significantly higher than that of individual poloxamer and CP1342 solutions at each shear rate. Furthermore,they showed the pseudoplastic behavior with hysteresis trader the physiologic condition;Based on the thermosensitive in situ gelling property of P407/P188 and the mucoadhesive property of CP1342,the two combined polymer solutions exhibited excellent mucoadhesive ability;In vitro release studies demonstrated diffusion-controlled release of puerarin from the combined solutions over a period of 8 h.(4) Diffusion behavior investigation of puerarin in the pharmaceutical preparationsThe free diffusion model was used in this investigation.The diffusion coefficient (D) of puerarin in the combined polymer gel was lower than those in P407/P188 and 0.2%CP1342.The D values decreased as the increase of the concentrations of these three polymers.The concentration of puerarin had no significant relevance with the D value.HPCD had little influence on the D value.With the increase of the temperature, the D values decreased.(5) The elimination of puerarin in tear and the initial pharmacodynamic evaluationThe results indicated that although the general trend of all the puerarin concentration versus time curves was similar,the puerarin concentration of the combined polymer gel was higher than that of puerarin-containing simulated tear fluid (STF)almost at each time point.TheAUC_{0â†'480 min} values of the two combined polymer gel were 4.43 times and 5.26 times greater than that of puerarin-contalning STF,respectively.The initial pharmacodynamic evaluation demonstrated that the combined polymer gel effectively prolonged the IOP-lowering effect to 24 h after administration,which was significantly better than STF(8 h) and relatively better than P407/P188 and CP1342(＞8 and＜24 h).The combined polymer gel gave significantly faster T_max of puerarin than did STF(P＜0.05).3.09-fold and 3.61-fold increase(P＜0.05) in AUC_{0â†'24 h} were obtained for the two combined polymer gel, respectively,relative to the STF.(6) The initial stability and the eye irritation investigation of the pharmaceutical preparationsThe initial stability investigation was performed.The results of the influential factor experiments indicated that the preparations should be preserved away from light and under shady place.The accelerated stability experiments demonstrated that they have satisfactory stability and possess validity duration up to 2 years.The results of the eye irritation experiments after administrated serious times per day indicated that there are no irritation for both the medication administration group and the control group,suggesting they have relatively high security.