Effect of Moisture Sorption on Free Volume and Relaxation of Spray Dried Dispersions: Relation to Drug Recrystallization.

The effect of vapor sorption on the free volume of drug-polymer spray-dried dispersions (SDDs) was investigated, along with the crystallization propensity of drug molecules in SDDs after exposure to humidity. Subsequently, the correlation of free volume change and relaxation time with drug recrystallization was examined. Four polymers, including polyvinylpyrrolidone, polyvinylpyrrolidone vinyl acetate copolymer, hydroxypropyl cellulose, and hydroxypropyl methylcellulose acetate succinate, and 2 drugs (indomethacin and ketoconazole) were selected for preparing SDDs.