Physicochemical characterization of spray-dried phenylbutazone polymorphs

A spray-drying method was applied to the recrystallization of phenylbutazone, and the resulting samples were examined by X-ray powder diffractometry, differential thermal analysis, IR spectrophotometry, scanning electron microscopy, and hot-stage photomicroscopy. Three different crystalline forms (delta, beta, and epsilon) could be prepared from methylene chloride solution by varying the drying temperature of sprayed droplets from 120 degrees C to 30 degrees C. Form epsilon, the fifth polymorph of phenylbutazone, was confirmed as a novel crystalline form which could not be prepared by recrystallization techniques. In this spray-drying system the composition of spray-dried samples was shown to be a function of the drying temperature. While the stable form delta was obtained at higher drying temperatures, form epsilon was obtained only under conditions affording a slower evaporation rate of the solvent. The dissolution properties of the pure modifications prepared by recrystallization techniques and the spray-dried samples were evaluated in simulated intestinal fluid. Form epsilon showed excellent in vitro availability and much higher solubility than any other of the forms.