Focused Beam Reflectance Measurement as a Complementary Tool for Monitoring Disintegration and Drug Release Processes of Sustained-Release Formulations: A Preliminary Investigation

Focused beam reflectance measurement (FBRM) has been used for investigating tablet dissolution behavior. However, few studies have used FBRM to analyze sustained-release formulations. In this study, we prepared tablets containing hydroxypropyl methylcellulose (HPMC), a widely used sustained-release excipient, and evaluated dissolution behavior using both conventional dissolution testing and FBRM. To assess the effect of drug solubility on FBRM parameters, we also compared acetaminophen (readily soluble in water) with ethenzamide (poorly soluble in water). Conventional dissolution testing revealed a difference of approximately 360 min among the different HPMC grades in the time required to reach 60% drug release, while FBRM detected an approximate threefold difference in the final particle counts. These findings suggest that FBRM is a useful analytical tool for elucidating the dissolution behavior of sustained-release formulations.