Spheronization of solid lipid extrudates

The objective of this study was the examination and development of a solvent-free spheronization process as a manufacturing tool for sustained release matrix spheres. Extrudates prepared from a binary lipid mixture with different amounts of Dynasan 114® and Witocan 42/44® and theophylline as model drug were processed in systematic spheronization experiments by varying pellet formulation and spheronizer-jacket temperature. The rounding procedure of the pellets was investigated by analyzing spot samples after different processing times. The obtained pellets were characterized according to their shape, size distribution, porosity and drug release properties. Round lipid pellets with a mean aspect ratio below 1.1 and a narrow particle size distribution with median equivalent diameters around 1.5 mm could be obtained. The pellets showed sustained drug release properties and porosities below 1%. The spheronization process was shown to be strongly temperature- and formulation dependent. The material temperature during the process was influenced by the adjusted jacket temperature and friction- and shear forces between the rounded particles; control of material temperature seems to pose the challenge in the investigated process.