Evaluation of colloidal solid dispersions: physiochemical considerations and in vitro release profile

Colloidal solid dispersion is an innovative breakthrough in the pharmaceutical industry that overcomes the solubility-related issue of poorly soluble drugs by using an amorphous approach and also the stability-related issue by means of a complex formation phenomenon using different carrier materials. In the present study, a newly developed adsorption method is introduced to incorporate a high-energy sulfathiazole-polyvinylpyrrolidone (Plasdone® K-29/32) solid dispersion on porous silicon dioxide (Syloid® 244FP). Different ternary systems of sulfathiazole-Plasdone® K-29/32-Syloid® 244FP were prepared (1:1:2, 1:1:3, and 1:2:2) and categorized depending on the mechanism by which Syloid® 244FP was incorporated. Modulated differential scanning calorimetry (MDSC), X-ray diffraction, Fourier transform infrared spectroscopy, and in vitro dissolution studies were conducted to characterize the ternary systems. The X-ray diffraction and MDSC data showed a lack of crystallinity in all internal and external ternary systems, suggesting a loss of the crystallinity of sulfathiazole compared to the physical mixtures. USP apparatus II was used to measure the in vitro dissolution rate of the prepared systems at 75 rpm in different media. The dissolution rate of the optimum ratio (1:2:2) containing an internal ternary solid dispersion system was found to be three times higher than that of the external and physical systems. Thus, the porous silicon dioxide incorporated into the conventional binary solid dispersion acted as a carrier to disperse the complex and increase the dissolution rate.