A surface-attached silymarin-loaded solid dispersion with improved dissolution profile and enhanced oral bioavailability was formulated using silymarin, polyvinylpyrrolidone (PVP) and Tween 80 in water. In this solid dispersion, hydrophilic PVP was adhered onto the surface of crystalline drug rendering silymarin hydrophilic without changing its crystallinity. The drug solubility from the optimised solid dispersion prepared with silymarin/PVP/Tween 80 at the weight ratio of 5/2.5/2.5 increased by almost 650-fold compared to drug powder. The drug was physically and chemically stable in the solid dispersion for at least 6 months. Moreover, the solid dispersion enhanced the oral bioavailability of the drug in rats by almost 3-fold compared to the commercial product. The silymarin-loaded solid dispersion also exhibited advanced hepatoprotective bioactivity against CCl4-induced liver damage compared to silymarin or the commercial product. Thus, this silymarin-loaded solid dispersion would be useful for the enhancement of oral bioavailability and hepatoprotective activity of poorly water-soluble silymarin.
Keywords: Bioavailability; hepatoprotection; silymarin; solid dispersion; solubility.