DEVELOPMENT AND VALIDATION OF STABILITY INDICATING RP-HPLC METHOD OF NEPAFENAC AND ITS DEGRADATION PRODUCTS: APPLICATION TO DEGRADATION KINETIC

Objective : The objective of present work was to develop and validate simple, precise, accurate and specific stability indicating method for determination of nepafenac in presence of its degradation products and application of the method to study degradation kinetics. Methods : A novel isocratic RP-HPLC method has been developed using C 8 Olyster column, (250X4.6 mm i. d, 5m particle size) with the mobile phase composition of ACN: 10 mM Ammonium formate buffer (pH 4.0): Methanol (27.5:45:27.5). The flow rate was at 1.0 ml min -1 and effluent was detected at 238 nm. Nepafeac was subjected to stress degradation under acid, base, neutral hydrolysis, oxidation, dry heat, humidity and photolysis, conditions. Kinetic study was also performed. Results: The degradants peaks were well resolved from Nepafenac peak. Significant degradation was observed in acid, base and oxidative degradation. The drug is relatively stable towards photolysis and dry heat. Conclusion: Stability of Nepafenac was determined by stability indicating assay method. Three degradation related impurities was identified by LC-MS. The hydrolytic degradation pathway of nepafenac was postulated. The developed stability indicating method was applied to determine acid, base and oxidative degradation kinetic. Acid hydrolysis and oxidative degradation followed zero order while base hydrolysis followed first order kinetic. Degradation rate constants and half-life were determined.