Adsorption of a poorly water-soluble drug onto porous calcium silicate by the sealed heating method

Abstract

To improve the bioavailability of orally-administered drug, solubilization of poorly water-soluble drug is important. The solubility of a drug in its amorphous form is known to be higher than in its crystalline form. In this study, we attempted to adsorb a sublimable drug onto porous calcium silicate (Florite®, FLR) or non-porous calcium silicate (NPCS) by the sealed heating (SH) method and evaporated (EV) method. Ibuprofen (IBU) was used as the poorly water-soluble, sublimable drug. The physicochemical properties of samples were investigated using powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and dissolution test. From the PXRD and DSC results, IBU crystals were adsorbed and amorphized by the SH and EV methods with FLR. From the results of FTIR, the shift to a higher frequency by the carbonyl stretching vibration band of IBU suggests an intermolecular interaction between IBU and FLR. In SH with FLR, improved solubilization was observed. IBU adsorbed onto FLR showed a greater dissolution rate than the IBU crystals or NPCS. Thus, the petal-like structure of FLR may be an effective method to adsorb IBU onto FLR using the SH method.

Keywords: Amorphous; Ibuprofen; Porous calcium silicate; Sealed heating; Sublimable drug.