Twin Screw Extrusion for Pharmaceutical Processes

Abstract

The use of twin screw extruders (TSEs) to create sophisticated dosage forms is expanding because the continuous melt extrusion (ME) process has been proven to be a consistent and repeatable way to make high-quality products. TSEs are continuous small mass continuous mixers that are the plastics industry’s preferred manufacturing methodology for compounding and devolatilization. It is without question that pharmaceutical companies have reaped the benefit of over half a century of technological developments and process refinement in plastics. It is only in the last decade or so that extrusion has emerged as a viable platform for pharmaceutical development.

This chapter will describe the design and functionality of co-rotating and counterrotating TSEs for pharmaceutical applications. Screw and process design to facilitate effective mixing are addressed. Control parameters and the associated interactions (i.e., screw rpm versus feed rate) to achieve a quality product are proffered. Common TSE terms are defined and examples of useful TSE formulas are presented and explained. Staging of unit operations in a TSE and downstream system functionalities are described. Case studies are also presented to provide insight into how melt extrusion is being applied today. Finally, potential future growth areas are identified for melt extrusion.