RESUMO
Compared to traditional drug release monitoring with manual sampling and testing procedures, low-field nuclear magnetic resonance (LF-NMR) imaging is a one-step, visual, non-destructive, and non-invasive measurement method. Here, we reported the application of LF-NMR to image the morphology, component, sub-diffusion, and spatial distribution of a solid oral formulation, Biyankang tablets, during dissolution in vitro. The drug ingredients with characteristic relaxation times were distinguished and localized based on the signal of standards, such as patchouli oil, Xanthium strumarium extract, and starch. The hydration, swelling, disintegration, and sub-diffusion of tablets in simulated gastric fluids (SGF) were visualized statically. All tablets showed similar expansion (37.4-42.0%) along the direction of thickness at 25 min and reached a full disintegration at 145 min, at pH 1.80-6.15, indicating pH-independent swelling and disintegration. Compared to that static immersion within 20 mL SGF, the tablet disintegration time was shortened by ~ 11% in 30 mL SGF. The application of shear reduced the time by ~ 28%, suggesting a major role of hydrodynamic condition in tablet dissolution. The ability to simultaneously visualize, distinguish, and localize drug ingredients using LF-NMR is expected to provide valuable information to develop drug release monitoring systems in vitro and potentially in vivo using small animal studies.
