Preparation Of Ophthalmic Ion-sensitive In Situ Gel And Its Evaluation

Objective:Ophthalmic in-situ gel of Pilocarpine Nitrate(PN)was prepared. The release behavior in vitro and the pharmacodynamics in rabbit were investigated and its quality standard was developed.Methods:(1)Ophthalmic in-situ gels of PN were prepared containing gellan gum at different concentration.Ion-sensitive gellan gum was used as the matrix of gel and PN was selected as a model drug.According to the first method of measuring release behavior in the second part of China Pharmacopeia(2005),drug release was determined from in-situ gels in artificial tears,and compared with the release from PN eye drop.The pharmacodynamics of in-situ gels in rabbit was evaluated by measuring intraocular pressure(IOP)and pupillary diameter.(2)High performance liquid chromatography was developed to determine the content of PN in in-situ gel. Analytical column was SHIM-PACK CLC-NH2(150 mm×4 mm,5 um).The mobile phase consisted of methanol.The mobile phase was delivered at a flow rate of 0.8 mL·min^-1.Detection was performed at wavelength of 211 nm under 40℃.And the stability of the optimal formulation was primarily studied by influential factor test, accelerated test and long-term test.Results:(1)PN was completely released from conventional eye drop within 3 h, while for the PN-containing 0.4%gellan gum the amount of PN released was about 68%within 3 h and rising to about 87%after 10 h.In vitro release of in-situ gels was in accordance with Ritger-Peppas equation.For formulations containing 0.1%,0.2% and 0.4%gellan gum,the IOP-lowering effect was prolonged to 6,7 and 10 h respectively,which was significantly superior to the control group(3 h),and 2.39-fold, 3.97-fold and 6.14-fold increase in area under drug effect-time curve(AUC)were obtained respectively,compared with the control group.The miotic response was prolonged to 7,8 and 10 h respectively,which was significantly superior to the control group(4 h),and 1.65-fold,2.55-fold and 3.15-fold increase in AUC were obtained respectively.The optimal formulation contains PN 1 g,gellan gum 0.4 g, ethylparaben 0.3 g and glycerol 1 g which were dissolved in water for injection to 100 mL.(2)Equation of linear regression for PN were A = 14185C - 43554 in the concentration(6.4～128μg·mL^-1)with r value of 0.9988.The average recovery of PN was 100.94%.The RSD of PN was lower than 2.87%for intra-day and inter-day assays.The content of the optimal formulation was decreased to 95.47%and 96.95% after 10 days under 40℃and illumination,respectively.The content of the optimal formulation was reduced to 72.04%and 95.14%after 3 months under 25℃and 4℃darkly,respectively.Conclusions:(1)Gellan gum could delay the release of PN from in-situ gels. The more concentration of gellan gum increased,the more amount of released drug decreased.The results of in vivo pharmacodynamics evaluation indicated that the residence time of drug was prolonged by in-situ gels in rabbit.(2)PN was tertiary amine compound and its instability resulted in the instability of the optimal formulation.It was sensitive to temperature and illumination and was instable under room temperature and refrigeration.There was further research on the stability of the preparation.Innovation:(1)The effect of gellan gum ophthalmic application on in vitro release and pharmacodynamics was investigated for the first time.(2)NP-HPLC was established to determine the content of PN for the first time.