The effect of cooling on the degree of crystallinity, solid-state properties, and dissolution rate of multi-component hot-melt extruded solid dispersions

The effect of cooling on the degree of crystallinity, solid-state and dissolution properties of multi-component hot-melt extruded solid dispersions [SD] is of great interest for the successful formulation of amorphous SDs and is an area that is unreported, especially in the context of improving the stability of these specific systems. The thermal solid-state properties, degree of crystallinity, drug–polymer interactions, solubility and physical stability over time were investigated. X-ray powder diffraction [XRPD] and hyper differential scanning calorimetry [DSC] confirmed that indomethacin [INM] was converted to the amorphous state; however, the addition of poloxamer 407 [P407] had a significant effect on the degree of crystallinity and the solubility of the SD formulations. Spectroscopy studies identified the mechanism of interaction and solubility studies, showing a higher dissolution rate compared to amorphous and pure INM in pH 1.2 with a kinetic solubility of 20.63 µg/mL and 34.7 µg/mL after 3 and 24 h. XRPD confirmed that INM remained amorphous after 5 months stability testing in solid solutions with Poly(vinylpyrrolidone-co-vinyl acetate) [PVP VA64] and Plasdone S-630 [PL-S630]. Although cooling had a significant effect on the degree of crystallinity and on solubility of INM, the cooling method used did not have any significant effect on the amorphous stability of INM over time.