Emergent composite structures following the amorphization of itraconazole with α-glucosyl rutin by over-grinding

Abstract

We investigated the use of α-glucosyl rutin (rutin-G) as a grinding aid for wet bead milling. Itraconazole (ITCZ), which has low solubility at physiological pH conditions, was used as a model poorly water-soluble drug. Pulverization of ITCZ with rutin-G effectively improved the dissolution profile of ITCZ relative to other grinding aids, whereas excess pulverization of ITCZ with rutin-G led to a decrease in the dissolution rate of ITCZ. The structures of these pulverized samples were evaluated by powder X-ray diffraction (PXRD) and small-angle X-ray scattering (SAXS) to better understand this unexplained phenomenon. The PXRD pattern of ITCZ with rutin-G after milling for 10h was dramatically different from the patterns of ITCZ ground for shorter times. The results imply that the molecular-level middle-range ordering of the rutin-G and ITCZ mixture was almost unchanged for different milling time increments up to 5h, whereas the sample milled for 10h showed structural changes in the middle-range order. Furthermore, an analysis of the SAXS measurements suggested a change in the composite structures from large μm-size particles through a molecular-level local atomic arrangement of each particle via a molecular reaction between ITCZ and rutin-G as the milling time progressed. The decrease in dissolution rate after 5h may be related to the formation of the new composite structures between ITCZ and rutin-G. Excess pulverization caused by the addition of rutin-G may induce structural changes in the drug undergoing milling.