Formulation optimization of nifedipine containing microspheres using factorial design

Nifedipine is a calcium channel blocker which is used in the treatment of hypertension angina pectoris. The aim of this study was to formulate and optimize nifedipine containing microspheres in an attempt to prepare a suitable sustained release delivery system using factorial design. Drug loaded microspheres were prepared using Eudragit RL100, through solvent evaporation technique. In the next step, the effect of different formulation variables, including the amount of polymer (1 - 2 g), stabilizer (0.1 - 0.5 g) and drug/polymer ratio (0.05:1 - 0.1:1) on the appearance, physical properties of particles, and the amount of loaded drug was investigated. Based on the type and the variables studied, 8 formulations were designed using factorial design method, and were then prepared and their drug contents were determined. In order to detect the precise effect of the formulation variables and their interactions, design expert software was used. Data analysis showed that microspheres with optimum drug loading could be prepared using 1 g polyvinylalcohol, 1 - 2 g polymer and 0.07:1 drug/polymer ratio. Among the formulations suggested and based on the predicted responses and their desirability indices, 6 formulations were selected as the optimum formulations. Finally, selected microspheres were evaluated from the view points of morphology and release pattern. Results revealed that microspheres obtained from the formulations S(19), S(20) and S(24) could be selected as the best and optimized formulations due to their high drug contents, appropriate invitro drug release after 12 h and desired morphology.