Multifractal Characterization of Pharmaceutical Hot-Melt Extrudates

Purpose Multifractal geometry has become a powerful tool to describe complex structures in many fields. Our first aim was to combine imaging and multifractal analysis to better understand the microstructure of pharmaceutical extrudates. A second objective was to study erosion/dispersion behavior of the formulations because it would condition release of any drug. Methods Different formulations containing a lipid, a polymer and different silica based inorganic carriers were produced by hot-melt extrusion at various screw speeds. Multifractal analysis was based on scanning electron microscopy/energy dispersive X-Ray spectroscopy images. This microstructural analysis was complemented with dynamic optical imaging of formulation erosion/dispersion behavior. Results Multifractal analysis indicated that inorganic carrier type and concentration as well as the screw speed affected the microstructure of the extrudates. The aqueous erosion/ dispersion study showed that only the type and concentration of inorganic carrier were important. Conclusions The use of microstructural and dispersion analysis appeared to be complementary to better characterize and understand complex formulations obtained by hot-melt extrusion.