ABSTRACT
Objective To study the effect of surfactants on the dissolution profiles of poorly water-soluble acidic drug nimesulide from sustained-release tablets.Methods The anionic surfactant sodium dodecyl sulfate (SDS), cationic sur-factant cetyltrimethyl ammonium bromide (CTAB) and nonionic surfactant polysorbate 80 (Tween 80) were used to prepare nimesulide micelles .The effect of the buffer , surfactant and ionic strength on the equilibrium solubility of the drug and the in vitro release of sustained-release tablets was studied .Results and Conclusion In pH 1.2 HCl solution, water and pH 6.8 phosphate buffer, the solubilization capacity of CTAB was the highest.However, in pH 9.0 Tris buffer, when CTAB concen-tration was at about 1%, the equilibrium solubility of nimesulide was at the trough value .The in vitro release results were similar to those of equilibrium solubility and the kinetic pattern conformed to the first order equation according to the coefficient R .
ABSTRACT
Objective To optimize the formulation of metoprolol succinate ( MS) controlled release pellets by central composite design-response surface methodology .Methods MS sustained-release pellets were prepared using sugar pellet cores as starter beads , ethyl cellulose as coating materials and MS itself as a pore former .The formulation of MS sustained-release pellets was optimized by a central composite design with two factors at five levels .These two factors ( two independ-ent variables) were the pore former level and coating level , and the evaluated indexes ( namely dependent variables ) included the in vitro cumulative release percentages of MS at 1, 4, 8, 12 and 16 h, respectively.Results and Conclusion The results of mathematical equation fitting suggested that the second-order quadratic model was the optimal fitting equa-tion.According to the response surfaces , the optimum values at the pore former level and coating level weve ranged from 16%to 18%and 20% to 25%, respectively .The in vitro cumulative release percentage of MS from the pellets at 1 h reached 9.15%,which consequently eliminated the lag phase in the initial release period and exhibited a good sustained-release effect.Central composite design-response surface methodology can be applied to optimizing the coating formulation for MS sustained release pellets .