Evaluation of solubility parameter to predict apparent solubility of amorphous and crystalline cefditoren pivoxil

The purpose of this study is to evaluate and predict the apparent solubility of cefditoren pivoxil in different crystallinity in terms of the two dimensional solubility parameters. The crystallinity of cefditoren pivoxil gradually decreased through grinding process. The partial solubility parameters, δ_d and δ_s relating to dispersion force interaction and other specific interaction, respectively, were calculated for the ground samples of cefditoren pivoxil using the inverse gas chromatography. The values of δ_d were constant independently regardless of the crystallinity, while the values of δ_s became greater with a decrease in the crystallinity of cefditoren pivoxil, suggesting that the polarity on the surface of cefditoren pivoxil powders could become higher. Interaction radius was calculated from the partial solubility parameters of cefditoren pivoxil and water. The dissolution study in water demonstrated that the concentration of cefditoren pivoxil at 20 min increased with decreasing in crystallinity. From these results, the improvement of dissolution by grinding should result from the change of the surface energetics relating to the polarity of cefditoren pivoxil by grinding. Further, the interaction radius could be also applied to predict the apparent solubility of crystalline cefditoren pivoxil in various organic solvents.