Nimodipine loaded PLGA nanoparticles: formulation optimization using factorial design, characterization and in vitro evaluation.

The present study was aimed at developing a sustained release formulation of Nimodipine (NIM) nanoparticles using the biodegradable polymers, poly (lactide-co-glycolide) (PLGA 50:50 and 85:15) as carrier. NIM is a widely used calcium channel blocker which has to be administered as an intravenous infusion for a prolonged period of 1-2 weeks in the treatment of cerebral vasospasm. A sustained release biodegradable formulation would serve to replace this conventional therapy of continuous intravenous administration. PLGA nanoparticles were prepared by a modified precipitation method using high pressure homogenizer at 10,000 to 14,000 psi. A 3(2) factorial design was applied for optimization of the formulation parameters and for studying the effect of two independent variables [drug: polymer ratio and concentration of surfactant (Pluronic F 127)] on entrapment efficiency and mean particle size (response variables). Contour plots were plotted which gave a visual representation of the two variables on the dependent variables and also indicated non-linear relationship between them. The nanoparticles had particle size of 131+/-1.9 nm for PLGA 50:50 and 196+/-2.2 nm for PLGA 85:15. Scanning Electron Microscopy studies indicated that nanoparticles had spherical shape with a regular surface. The nanoparticles had high entrapment efficiency (96.42+/-2.09% for PLGA 50:50 and 94.50+/-1.25% for PLGA 85:15). DSC thermograms indicated that NIM was dispersed as an amorphous state in the nanoparticles. In vitro drug release from the lyophilized nanoparticles showed 94.35 +/- 3.8% NIM release from PLGA (50:50) nanoparticles and 63.32 +/- 4.6% release from PLGA (85:15) nanoparticles in 25 days. The release was first ordered and fickian diffusion kinetics in both the cases. These preliminary results indicate that NIM loaded PLGA nanoparticles could be effective in sustaining its release for a prolonged period. However, further studies are needed to confirm its performance in vivo.