A review of twin screw wet granulation mechanisms in relation to granule attributes

Due to the trend of continuous pharmaceutical manufacturing, twin screw wet granulation (TSWG), a continuous process, has gained increased research interest as a potential substitution of traditional batch granulation processes. Despite the complex nature of TSWG, its mechanisms have been gradually unveiled with the aid of innovative research strategies. This review synthesizes these recent findings to provide a comprehensive and mechanistic understanding of TSWG. We explain the impact of screw profiles (i.e. conveying, kneading, turbine mixing, and screw mixing elements) and process conditions (i.e. screw speed, feed rate, and liquid-to-solid ratio) on TSWG mixing performance and granule growth along the barrel, both of which ultimately affect critical granule attributes such as content uniformity, size distribution, strength, and compaction properties.