Preparation and characterization of nitrendipine solid lipid nanoparticles.

Nitrendipine, a dihydropyridine calcium channel blocker, has very poor oral bioavailability (10-20%) due to first pass effect. Solid lipid nanoparticle (SLN) delivery systems of nitrendipine have been developed using various triglycerides (trimyristin, tripalmitin and tristearin), soy phosphatidylcholine 95%, poloxamer 188 and charge modifiers stearylamine and dicetyl phosphate. SLNs were prepared by hot homogenization of melted lipids and aqueous phase followed by ultrasonication at temperatures above the melting point of lipids. Optimization studies of process and formulation variables were carried out. Particle size and zeta potential were measured by photon correlation spectroscopy (PCS) using Malvern zetasizer. Differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) studies were performed to characterize state of drug and lipid modification. In vitro release studies were performed in phosphate buffer pH 6.8 using modified Franz diffusion cell. Stable nitrendipine SLNs of mean size range 79 to 213 nm and zeta potential -38.2 to +34.6 mV were developed. About 99% nitrendipine was entrapped in SLNs and were stable on storage at 4 and 25 degrees C. DSC and PXRD analyses revealed that nitrendipine is dispersed in SLNs in an amorphous state. The release pattern of drug is analyzed and found to follow Weibull distribution rather than first order and Higuchi equation.