Preparation and evaluation of pilocarpine nitrate in situ gel for ophthalmic use / 中草药

ABSTRACT

Objective To develop and charaterize a series of Poloxamer-and Carbopol-based in situ gel for ophthalmic use as to enhance the ability of drug to retain in eyes and delay drug release.Methods The gel was prepared using Poloxamer 407/188 and Carbopol 974P as gelling agent and viscosity enhancer,respectively.Rheological characteristics were evaluated and behaviour of drug release in vitro was investigated by modified Franz diffusion cells.Results The rheological study indicated that the gel was physically entangled polymer solutions at 20 ℃ and then converted into a network structure with secondary bonds at 35 ℃.The gel released the drug molecules slowly in 4 h.The best fit model was Higuchi matrix model(r=0.992 3).Formulations consisting of Poloxamer 188 and Carbopol 974P were proved to be able to decrease the drug release speed efficiently.The impact on elastic modulus G" of the gel caused by those two were different.Conclusion An in situ gel with suitable sol-gel transition temperature and satisfactory release pattern could be achieved by adjusting the ratio of Poloxamer 407 to Poloxamer 188.The developed formulations have the ability to prolong the ocular residence time,which suggests it may be a new durg delivery system with bright future.