Application of continuous twin screw granulation for the metformin hydrochloride extended release formulation

This study focuses on evaluating the potential of transferring from a batch process to continuous process for manufacturing of the extended release formulation. Metformin hydrochloride (HCl) was used in the model formulation which was intended to contain the high amount of hydrophilic drug. The effects of barrel temperature, binder type, powder feed rate, and screw speed on granule properties (size and strength) and torque value in twin screw granulation were investigated. Due to the high content of hydrophilic model drug, the granules prepared at a higher temperature with HPMC binding solution had the narrower size distribution and greater strength than the granules prepared with distilled water as a binding solution. After continuous drying and milling steps, the granules (continuous process) satisfied the fundamental purpose of granulation with size and flowability, despite different shape compared with the granules (batch process). Furthermore, there were no significant differences between two granulation processes in tablet properties, such as tablet hardness and in vitro release. The considerations and strategies used in this study to transfer from a batch to continuous process can be applied to other existing formulations based on high shear granulation to enable rapid process transfer in the pharmaceutical industry.