Dissolution Rates of Finely Divided Drug Powders II: Micronized Methylprednisolone

Abstract

The dissolution rate of micronized methylprednisolone in aqueous solutions was measured. Also, the particle size distribution was measured and an approximate distribution function was found. This function was incorporated into the theory for the diffusion-controlled dissolution of finely divided heterodisperse powders. The reasonably good agreement between experiment and theory suggests that the rate-determining step, in this instance, is diffusion of the drug in the aqueous phase. The possible effects of agitation, sedimentation, particle shapes, and the variation of solubility with particle size have been considered. The composite effects of these may account for the deviations between experiment and theory. The dissolution rate of micronized methylprednisolone in aqueous solutions was measured. Also, the particle size distribution was measured and an approximate distribution function was found. This function was incorporated into the theory for the diffusion-controlled dissolution of finely divided heterodisperse powders. The reasonably good agreement between experiment and theory suggests that the rate-determining step, in this instance, is diffusion of the drug in the aqueous phase. The possible effects of agitation, sedimentation, particle shapes, and the variation of solubility with particle size have been considered. The composite effects of these may account for the deviations between experiment and theory.