The Science and Practice of Extrusion-Spheronization

Abstract

Extrusion-spheronization is one of the important techniques for pellet production. In most cases, the extruded-spheronized pellets are then coated with a functional coating. Extrusion-spheronization is a robust process and allows high drug loading of the pellets. The mean particle size is mainly determined by the die diameter, and its distribution is usually controlled to obtain a narrow particle size distribution. A pelletization aid is required to allow extrusion and spheronization of drugs, and microcrystalline cellulose (MCC) is the standard pelletization aid used in the industry. Different models have been used to explain the functionality of MCC. However, in certain cases MCC may not be suitable for this application, for example, in the case of drugs with low solubility, it may lead to slower drug release. In these cases, alternative pelletization aids like carrageenan or crospovidone have been studied. In recent years, the scale-down for early formulation development was in focus, and therefore, small-scale extruders and spheronizers have been developed. In case of twin-screw extruders, the feeding systems are of high importance with respect to constant product quality. The extrusion process control and application of process analytical technologies (PAT) have made significant progress. In addition, in recent years the spheronization process is better understood.