Preparation and evaluation of andrographolide solid dispersion vectored by silicon dioxide

Background: Andrographolide (Andro) is a “natural antibiotic” as well as a typical insoluble drug. The purpose of this study was to investigate the feasibility of commercially available silica (SiO₂) as a carrier of solid dispersion to enhance the dissolution of Andro. Materials and Methods: The solvent evaporation method was adopted, and a series of process parameters were studied to prepare a solid dispersion. Andro, SiO₂, physical mixture, and solid dispersion were characterized with respect to particle size distribution, special surface area, pore volume, and scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction studies. Results: Single factor test suggested the best preparation of solid dispersion was the drug and carrier (SiO₂B) ratio of 1:8, with tetrahydrofuran as the solvent, and a recovery temperature of 50°C. Compared to crude drug and mixture, solid dispersion was found to form a unique structure to disperse the drug and displayed superior performance in rapid dissolution. Conclusion: The present study signifies the commercially available SiO₂is an excellent but cheap carrier to improve the dissolution of Andro. Our results provide a highly operability approach for improving the dissolution of insoluble natural products and are beneficial for the clinical effects improvement.